### Install and Run Development Server

Source: https://github.com/yowainwright/es-check/blob/main/site/README.md

Install project dependencies and start the development server using pnpm.

```bash
pnpm install

pnpm dev
```

--------------------------------

### Example package.json Browserslist Configuration

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/browserslist.mdx

An example of the browserslist configuration within a package.json file.

```json
{
  "browserslist": ["last 2 versions", "> 1%", "not dead"]
}
```

--------------------------------

### Example .browserslistrc Configuration

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/browserslist.mdx

An example of a .browserslistrc file defining target browsers.

```plaintext
# Browsers we support
last 2 versions
> 1%
not dead
```

--------------------------------

### ES Check Configuration File Example

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/performance.mdx

Use a .escheckrc configuration file to manage complex setups, including ECMAScript version, file paths, exclusions, and batch size. This centralizes settings for repeatable builds.

```json
// .escheckrc
{
  "ecmaVersion": "es5",
  "files": ["./dist/**/*.js"],
  "not": ["./dist/vendor/**"],
  "batchSize": 50
}
```

--------------------------------

### Environment-Specific Browserslist Config Example

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/browserslist.mdx

Example of environment-specific configurations within a browserslist file.

```plaintext
[production]
> 0.5%
last 2 versions
Firefox ESR
not dead

[development]
last 1 chrome version
last 1 firefox version
```

--------------------------------

### Configuration File Example

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Example of an .escheckrc JSON configuration file, detailing various options for customizing ES Check behavior.

```json
{
  "ecmaVersion": "es6",
  "module": false,
  "files": "./dist/**/*.js",
  "not": ["./dist/skip/*.js"],
  "allowHashBang": false,
  "looseGlobMatching": false,
  "checkFeatures": true,
  "checkForPolyfills": true,
  "ignorePolyfillable": "core-js",
  "ignore": ["ErrorCause", "TopLevelAwait"],
  "allowList": ["ArrayToSorted", "ObjectHasOwn"],
  "checkBrowser": false,
  "browserslistQuery": "last 2 versions",
  "browserslistPath": "./config/.browserslistrc",
  "browserslistEnv": "production"
}
```

--------------------------------

### Quick Start: Check Files Against ES5

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/gettingstarted.mdx

Use the quick start command to check if files in specified directories match the ES5 version. ES Check will report any files that do not pass the check.

```bash
es-check es5 './vendor/js/*.js' './dist/**/*.js'
```

--------------------------------

### Install ES Check Globally with yarn

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/installation.mdx

Install ES Check globally for system-wide availability using yarn.

```bash
yarn global add es-check
```

--------------------------------

### ES Check Configuration File Example

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/configuration.mdx

Create a .escheckrc file in your project root to define consistent settings.

```json
{
  "ecmaVersion": "es6",
  "module": false,
  "files": "./dist/**/*.js",
  "not": ["./dist/skip/*.js"],
  "allowHashBang": false,
  "checkFeatures": true
}
```

--------------------------------

### Install ES Check Globally with npm

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/installation.mdx

Install ES Check globally for system-wide availability using npm.

```bash
npm install -g es-check
```

--------------------------------

### Example Ignore-Features JSON File

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/options.mdx

An example JSON file structure for specifying features to ignore when using the `--ignoreFile` option.

```json
["TopLevelAwait", "ErrorCause", "PrivateClassFields"]
```

--------------------------------

### CI/CD Integration Example

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/quickstart.mdx

Example of how to integrate ES Check into a GitHub Actions workflow to automatically verify JavaScript compatibility on every run.

```yaml
# Example GitHub Actions
- name: Check ES Version
  run: npx es-check es5 './dist/**/*.js'
```

--------------------------------

### Package.json Scripts for CI

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/ci-integration.mdx

Example package.json scripts to define build, test, and ES version check commands for CI integration.

```json
{
  "scripts": {
    "build": "webpack",
    "test": "jest",
    "check:es": "es-check es5 './dist/**/*.js'",
    "ci": "npm run build && npm run test && npm run check:es"
  }
}
```

--------------------------------

### Install ES Check Globally

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Install ES Check globally for command-line access on your system.

```sh
npm i es-check -g
```

--------------------------------

### Configuration File Setup

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/quickstart.mdx

Configure ES Check using a `.escheckrc` file for persistent settings. This allows you to define the ECMAScript version, target files, and exclusions.

```json
{
  "ecmaVersion": "es5",
  "files": ["./dist/**/*.js"],
  "not": ["./dist/modern/**/*.js"]
}
```

--------------------------------

### Install ES Check Locally or Globally

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/gettingstarted.mdx

Install ES Check as a development dependency in your project or globally for command-line access.

```bash
npm i es-check --save-dev   # locally
npm i es-check -g           # or globally
```

--------------------------------

### Example: Polyfill Detection Output

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/polyfills.mdx

Compare the output of ES Check with and without the `--checkForPolyfills` option to see how polyfill warnings are displayed.

```bash
# Without polyfill detection
es-check es5 './dist/app.js'
# ✓ Passed (but might include polyfills)

# With polyfill detection
es-check es5 './dist/app.js' --checkForPolyfills
# ⚠ Warning: Array.prototype.includes polyfilled (ES7 feature)
```

--------------------------------

### GitHub Actions with --light Mode

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/ci-integration.mdx

Example GitHub Actions step using `--light` mode for faster ES version checks in CI.

```yaml
# GitHub Actions with --light mode
- name: Fast ES5 compatibility check
  run: npx es-check es5 './dist/**/*.js' --light
```

--------------------------------

### ES Check Configuration File (.escheckrc)

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/browserslist.mdx

Example of an .escheckrc configuration file specifying checkBrowser, browserslistQuery, browserslistEnv, and files.

```json
{
  "checkBrowser": true,
  "browserslistQuery": "> 1%, last 2 versions",
  "browserslistEnv": "production",
  "files": "./dist/**/*.js"
}
```

--------------------------------

### Verify Global ES Check Installation

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/installation.mdx

Verify that ES Check is installed correctly globally by checking its version directly.

```bash
es-check --version
```

--------------------------------

### Verify Local ES Check Installation

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/installation.mdx

Verify that ES Check is installed correctly locally by checking its version using npx.

```bash
npx es-check --version
```

--------------------------------

### Configure Batch Processing for Concurrency

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/performance.mdx

Examples of using the --batchSize option to control the number of files processed concurrently, including unlimited parallelism.

```bash
# Process all files in parallel (default)
es-check es5 './dist/**/*.js' --batchSize 0

# Process 10 files at a time
es-check es5 './dist/**/*.js' --batchSize 10

# Process 50 files at a time
es-check es5 './dist/**/*.js' --batchSize 50
```

--------------------------------

### Source Map Version 3 Structure

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/source-maps.mdx

Example of the required fields in a Source Map v3 file.

```json
{
  "version": 3,
  "sources": [...],
  "mappings": "..."
}
```

--------------------------------

### Install ES Check Locally with npm

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/installation.mdx

Install ES Check as a development dependency in your project using npm. This ensures consistent version usage across your team.

```bash
npm install es-check --save-dev
```

--------------------------------

### Basic Usage: Check Files Against ES6

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/gettingstarted.mdx

Perform basic checks on JavaScript files against a specified ECMAScript version. This example checks files in a single directory and multiple directories for ES6 compatibility.

```bash
# Check single directory
es-check es6 ./js/*.js

# Check multiple directories
es-check es6 ./js/*.js ./dist/*.js
```

--------------------------------

### Install ES Check Locally with yarn

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/installation.mdx

Install ES Check as a development dependency in your project using yarn. This ensures consistent version usage across your team.

```bash
yarn add es-check --dev
```

--------------------------------

### Check Node Modules with ES Check

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/debugging.mdx

Example command to run ES Check on JavaScript files within the node_modules directory, useful for identifying issues in third-party packages.

```bash
# Check node_modules
es-check es5 './node_modules/problematic-package/dist/*.js'
```

--------------------------------

### ES Check Success Output

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/quickstart.mdx

Example of the output when all JavaScript files pass the ES compatibility check. Indicates successful validation.

```bash
✓ ES Check passed! All files are ES5 compatible.
```

--------------------------------

### ES Check Command-line Priority Over Config

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/configuration.mdx

Command-line arguments override configuration file settings. This example uses 'es6' from the command line, overriding any 'ecmaVersion' in the config file.

```bash
es-check es6 --config=.escheckrc
```

--------------------------------

### GitHub Actions CI Workflow

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/ci-integration.mdx

Example GitHub Actions workflow to automate ES version checking on push or pull request events.

```yaml
name: ES Version Check
on: [push, pull_request]

jobs:
  es-check:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Setup Node.js
        uses: actions/setup-node@v4
        with:
          node-version: "20"

      - name: Install dependencies
        run: npm ci

      - name: Build project
        run: npm run build

      - name: Check ES5 compatibility
        run: npx es-check es5 './dist/**/*.js'
```

--------------------------------

### ES Check Failure Output

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/quickstart.mdx

Example of the output when ES Check detects compatibility issues. Lists the files with violations and the specific ES6 features used.

```bash
✗ ES Check failed!
./dist/app.js - Uses ES6 feature: arrow function (line 10)
./dist/utils.js - Uses ES6 feature: const declaration (line 5)
```

--------------------------------

### Programmatic API: Run Checks

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Example of using the ES Check programmatic API in Node.js to run checks with custom configurations. Handles success and error reporting.

```javascript
const { runChecks, loadConfig } = require("es-check");

async function checkMyFiles() {
  const configs = [
    {
      ecmaVersion: "es5",
      files: ["dist/**/*.js"],
      module: false,
      checkFeatures: true,
    },
  ];

  const result = await runChecks(configs);

  if (result.success) {
    console.log("All files passed ES5 check!");
    // Output: All files passed ES5 check!
  } else {
    console.error(`ES Check failed with ${result.errors.length} errors`);
    result.errors.forEach((error) => {
      console.error(`- ${error.file}: ${error.err.message}`);
    });
    // Example output:
    // ES Check failed with 2 errors
    // - dist/app.js: Unsupported features used: const, arrow-functions but your target is ES5.
    // - dist/utils.js: Unsupported features used: template-literals but your target is ES5.
  }

  return result;
}
```

--------------------------------

### Detailed Error Handling with Node API

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/programmatic-api.mdx

Programmatically handle errors returned by `runChecks`. This example shows how to iterate through errors, log details, and exit with a non-zero status code if checks fail.

```javascript
const { runChecks } = require("es-check");

async function detailedErrorHandling() {
  const configs = [
    {
      ecmaVersion: "es5",
      files: ["dist/**/*.js"],
    },
  ];

  const result = await runChecks(configs);

  if (!result.success) {
    console.error(`ES Check found ${result.errors.length} incompatible files:\n`);

    result.errors.forEach((error, index) => {
      console.error(`${index + 1}. File: ${error.file}`);
      console.error(`   Error: ${error.err.message}`);

      if (process.env.DEBUG) {
        console.error(`   Stack: ${error.stack}`);
      }
    });

    process.exit(1);
  }

  console.log("All files passed ES5 compatibility check!");
}
```

--------------------------------

### Build and Preview Production Site

Source: https://github.com/yowainwright/es-check/blob/main/site/README.md

Build the project for production and preview the built site.

```bash
pnpm build

pnpm preview
```

--------------------------------

### Load Configuration from File Programmatically

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/programmatic-api.mdx

Demonstrates how to use the `loadConfig` function to load ES Check configurations from a file (e.g., `.escheckrc`) and then use these configurations with `runChecks`.

```javascript
const { runChecks, loadConfig } = require("es-check");

async function checkWithConfigFile() {
  // Load config from .escheckrc or custom path
  const configs = await loadConfig("./.escheckrc");

  // Run checks without a logger (silent mode)
  const result = await runChecks(configs);

  if (!result.success) {
    console.error("ES Check failed!");
    // Handle errors programmatically
    return { success: false, errors: result.errors };
  }
  return { success: true };
}
```

--------------------------------

### Theme Management and Initial Loader Styling

Source: https://github.com/yowainwright/es-check/blob/main/site/index.html

This snippet demonstrates how to manage theme settings using localStorage and apply styles for an initial loading state. It includes CSS for a spinner animation.

```javascript
const theme = localStorage.getItem("theme") || (window.matchMedia("(prefers-color-scheme: dark)").matches ? "dark" : "light");
document.documentElement.setAttribute("data-theme", theme);
```

```css
#root { min-height: 100vh; }
.initial-loader { min-height: 100vh; display: flex; align-items: center; justify-content: center; background: var(--fallback-b1, oklch(var(--b1))); }
.initial-loader::after { content: ""; width: 2rem; height: 2rem; border: 2px solid transparent; border-top-color: #4486c6; border-radius: 50%; animation: spin 0.6s linear infinite; }
@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}
```

--------------------------------

### Multiple Configurations for Different Bundles

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Use an array of configuration objects to specify different settings for various bundle types like UMD, CJS, and ESM. This allows tailored checks for each module format.

```json
[
  {
    "ecmaVersion": "es6",
    "module": false,
    "files": "{cjs,umd}/index.{cjs,js}"
  },
  {
    "ecmaVersion": "es2020",
    "module": true,
    "files": "esm/index.mjs",
    "checkFeatures": true
  },
  {
    "files": "legacy/*.js",
    "checkBrowser": true,
    "browserslistEnv": "legacy"
  }
]
```

--------------------------------

### Enable Lightweight Mode

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/options.mdx

Utilize the `--light` flag for faster checking by employing pattern matching instead of full AST parsing. This mode is ideal for CI/CD pipelines where performance is critical.

```bash
es-check es5 './dist/**/*.js' --light
```

--------------------------------

### Basic Browserslist Query

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/browserslist.mdx

Use the --checkBrowser flag with a specific browserslist query to check ES version compatibility.

```bash
es-check --checkBrowser --browserslistQuery="last 2 versions" ./dist/**/*.js
```

--------------------------------

### Using Project's Browserslist File

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/browserslist.mdx

ES Check automatically detects and uses your project's .browserslistrc or package.json browserslist configuration if present.

```bash
es-check checkBrowser ./dist/**/*.js
```

--------------------------------

### Browserslist Environments

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/browserslist.mdx

Use the --browserslistEnv flag to specify a particular environment for your browserslist configuration.

```bash
es-check --checkBrowser --browserslistEnv="production" ./dist/**/*.js
```

--------------------------------

### Multiple ES Check Configurations

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/configuration.mdx

For projects with different build targets, use an array configuration to specify multiple settings.

```json
[
  {
    "ecmaVersion": "es5",
    "files": "dist/legacy/**/*.js"
  },
  {
    "ecmaVersion": "es2020",
    "module": true,
    "files": "dist/modern/**/*.js"
  }
]
```

--------------------------------

### Enable Verbose Mode for ES Check

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/debugging.mdx

Use the --verbose flag to get more detailed output from ES Check, aiding in pinpointing issues.

```bash
es-check es5 './dist/**/*.js' --verbose
```

--------------------------------

### Run ES5 Compatibility Checks Programmatically

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/programmatic-api.mdx

Demonstrates basic usage of `runChecks` to verify ES5 compatibility for specified files. It shows how to handle the success and error results returned by the function.

```javascript
const { runChecks, loadConfig } = require("es-check");

async function checkES5Compatibility() {
  const configs = [
    {
      ecmaVersion: "es5",
      files: ["dist/**/*.js"],
      module: false,
      checkFeatures: true,
    },
  ];

  // Run without a logger (silent mode)
  const result = await runChecks(configs);

  if (result.success) {
    console.log("✅ All files are ES5 compatible!");
  } else {
    console.error(`❌ ES5 compatibility check failed with ${result.errors.length} errors`);
    result.errors.forEach((error) => {
      console.error(`  - ${error.file}: ${error.err.message}`);
    });
    // Example output:
    // ES version mismatch detected
    // dist/legacy/app.js: Unsupported features used: const, let but your target is ES5.
    // dist/modern/polyfills.js: Unsupported features used: top-level-await but your target is ES2020.
    return { success: false, errors: result.errors };
  }
}
```

--------------------------------

### ES Check Error with Source Maps

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/debugging.mdx

Example of an ES Check error message when source maps are enabled, showing original source file locations.

```bash
ES-Check Error:
----
· erroring file: src/components/Button.js at src/components/Button.js:10:5
· error: Unexpected token
```

--------------------------------

### Build and Run ES-Check Benchmarks with Docker

Source: https://github.com/yowainwright/es-check/blob/main/tests/benchmarks/README.md

Builds a Docker image for the ES-Check benchmarks and then runs the benchmarks within the container. This is the primary method for executing the performance tests.

```bash
docker build -t es-check-benchmark -f tests/benchmarks/Dockerfile .
docker run --rm es-check-benchmark
```

--------------------------------

### Use Browserslist with Custom Query and Feature Checking

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Combine browser compatibility checks with feature checks using a custom browserslist query.

```sh
es-check --checkBrowser --browserslistQuery=">0.5%, not dead" --checkFeatures ./dist/**/*.js
```

--------------------------------

### Run ES Check Performance Benchmarks

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/performance.mdx

Commands to clone the ES Check repository and run the performance benchmarks to compare tools and observe improvements.

```bash
git clone https://github.com/yowainwright/es-check.git
cd es-check
node benchmarks/generate-test-files.js 100 ./benchmarks/test-files
node benchmarks/compare-tools.js 3 ./benchmarks/test-files
```

--------------------------------

### CLI Usage with Tab Completion

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/options.mdx

Demonstrates how to use tab completion with the es-check CLI to discover available commands, versions, and options after setting up shell completion.

```bash
es-check <TAB>
```

```bash
es-check es6 --<TAB>
```

```bash
es-check --check<TAB>
```

--------------------------------

### Using a Custom ES Check Config Path

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/configuration.mdx

Specify a custom configuration file location using the --config flag.

```bash
es-check --config=./config/es-check-production.json
```

--------------------------------

### Custom ES Compatibility Testing

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/programmatic-api.mdx

Incorporate ES compatibility checks into your testing suite. This example shows how to use `runChecks` within a Jest test case to ensure ES5 compliance.

```javascript
const { runChecks } = require("es-check");

describe("ES Compatibility", () => {
  it("should be ES5 compatible", async () => {
    const configs = [
      {
        ecmaVersion: "es5",
        files: ["dist/**/*.js"],
        checkFeatures: true,
      },
    ];

    const result = await runChecks(configs);

    expect(result.success).toBe(true);
    expect(result.errors).toHaveLength(0);
  });
});
```

--------------------------------

### Configuration Options for ES Check

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/programmatic-api.mdx

Lists and explains the available configuration options for ES Check, mirroring the CLI arguments, for use in programmatic checks.

```javascript
const config = {
  ecmaVersion: "es5", // ES version to check against
  files: ["dist/**/*.js"], // Files to check (array or string)
  module: false, // Use ES modules
  allowHashBang: false, // Allow hashbang comments
  checkFeatures: true, // Check for ES version specific features
  checkForPolyfills: false, // Consider polyfills when checking
  not: ["**/vendor/*.js"], // Files/folders to exclude
  looseGlobMatching: false, // Don't fail if no files found
  ignore: "ErrorCause,TopLevelAwait", // Features to ignore
  allowList: "const,let", // Features to allow in lower ES versions
  batchSize: 0, // Files to process concurrently (0 = unlimited)
};
```

--------------------------------

### Specify Custom Configuration File Path

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Use the `--config` command-line option to point to a custom configuration file. This is useful for managing different configurations for various environments or test scenarios.

```sh
es-check --config=./configs/my-custom-config.json
```

--------------------------------

### Set Up Upstream Remote

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/how-to-contribute.mdx

Add the original ES Check repository as an upstream remote. This allows you to fetch updates from the main project.

```bash
git remote add upstream https://github.com/yowainwright/es-check.git
```

--------------------------------

### Specify Custom Configuration File

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/options.mdx

Use the `--config` option to point to a custom `.escheckrc` configuration file.

```bash
es-check --config=./configs/production.escheckrc.json
```

--------------------------------

### Common Browserslist Query: Mobile First

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/browserslist.mdx

A common browserslist query prioritizing mobile browser versions for iOS and Android.

```bash
--browserslistQuery="last 2 iOS versions, last 2 Android versions"
```

--------------------------------

### Run ES Check with Configuration

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/quickstart.mdx

Execute ES Check using the settings defined in the `.escheckrc` configuration file. This simplifies command-line usage by omitting explicit arguments.

```bash
npx es-check
```

--------------------------------

### Basic CLI Usage with Array of Arguments

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Basic command-line usage of es-check specifying an ECMAScript version and multiple file arguments.

```sh
es-check es6 ./js/*.js ./dist/*.js
```

--------------------------------

### Other ES Check Options

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/options.mdx

Includes options for loose glob matching, displaying version information (`--version` or `-V`), and showing help messages (`--help` or `-h`).

```bash
# Show version information
es-check --version

# Show help message
es-check --help
```

--------------------------------

### Process Files with Unlimited Batch Size (Default)

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Process all files in parallel by setting --batchSize to 0. This is the default behavior and is recommended for small codebases to maximize parallelism.

```sh
# Process all files in parallel (default)
es-check es5 './dist/**/*.js' --batchSize 0
```

--------------------------------

### Enable and Disable File Caching

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/performance.mdx

Demonstrates how to use ES Check with file caching enabled (default) and how to disable it if necessary.

```bash
# Cache is enabled by default
es-check es5 './dist/**/*.js'

# Disable cache if needed
es-check es5 './dist/**/*.js' --noCache
```

--------------------------------

### esbuild Source Map Configuration

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/source-maps.mdx

Use esbuild to bundle and generate source maps for your JavaScript files.

```sh
esbuild src/index.js --bundle --sourcemap --outfile=dist/bundle.js
```

--------------------------------

### Check Browser as ES Version

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/browserslist.mdx

Alternatively, use 'checkBrowser' directly as the ES version argument with a browserslist query.

```bash
es-check checkBrowser ./dist/**/*.js --browserslistQuery=">0.5%, not dead"
```

--------------------------------

### Fast Mode for CI/CD

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/quickstart.mdx

Enable faster checking in CI/CD pipelines by using the `--light` mode. This mode optimizes performance for automated environments.

```bash
npx es-check es5 './dist/**/*.js' --light
```

--------------------------------

### Check Browser Compatibility using ES Version Argument

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Use 'checkBrowser' as the ES version argument along with --browserslistQuery to check compatibility against your project's targeted browsers.

```sh
es-check checkBrowser --browserslistQuery="last 2 versions" ./dist/**/*.js
```

--------------------------------

### Progressive Enhancement with Fallbacks

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/debugging.mdx

Illustrates a JavaScript pattern for progressive enhancement, providing fallbacks for features like Promises.

```javascript
// Instead of failing, provide fallbacks
if (typeof Promise !== "undefined") {
  // Use Promise-based code
} else {
  // Use callback-based code
}
```

--------------------------------

### Check Multiple Directories

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/quickstart.mdx

Perform ES5 compatibility checks across multiple directories simultaneously. This is useful for verifying both project-specific and third-party code.

```bash
npx es-check es5 './vendor/**/*.js' './dist/**/*.js'
```

--------------------------------

### Custom Browserslist Config Path

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/browserslist.mdx

Specify a custom path to your browserslist configuration file when it's not in the default location.

```bash
es-check --checkBrowser --browserslistPath=./config/.browserslistrc ./dist/**/*.js
```

--------------------------------

### ES Check with Polyfill Detection

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/performance.mdx

Command for full compatibility analysis, including syntax checks, feature detection, and polyfill requirements.

```bash
es-check es5 './dist/**/*.js' --checkFeatures --checkForPolyfills
```

--------------------------------

### Run Checks with the Built-in Logger

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/programmatic-api.mdx

Demonstrates using ES Check's `createLogger` utility to generate a logger instance with configurable options like verbosity and color output, then passing it to `runChecks`.

```javascript
const { runChecks, createLogger } = require("es-check");

async function checkWithBuiltInLogger() {
  const configs = [
    {
      ecmaVersion: "es5",
      files: ["dist/**/*.js"],
    },
  ];

  // Create a logger with specific settings
  const logger = createLogger({
    verbose: true, // Show debug messages
    quiet: false, // Show all messages
    silent: false, // Output to console
    noColor: false, // Use colors in output
  });

  // Pass the logger in an options object
  const result = await runChecks(configs, { logger });

  if (!result.success) {
    // Handle errors programmatically
    return { success: false, errors: result.errors };
  }
  return { success: true };
}
```

--------------------------------

### Checking Bundled vs. Source Files with ES Check

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/performance.mdx

Checking a single bundled file is generally faster than checking many individual source files. This is due to reduced file system operations and overhead.

```bash
# Faster - one large file
es-check es5 './dist/bundle.min.js'

# Slower - many small files
es-check es5 './src/**/*.js'
```

--------------------------------

### CircleCI Configuration

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/ci-integration.mdx

CircleCI configuration to set up Node.js environment, build the project, and check ES version compatibility.

```yaml
version: 2.1
jobs:
  es-check:
    docker:
      - image: cimg/node:20.0
    steps:
      - checkout
      - run: npm ci
      - run: npm run build
      - run:
          name: Check ES Version
          command: npx es-check es5 './dist/**/*.js'
```

--------------------------------

### Run Benchmarks

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Execute benchmark tests to compare ES Check's performance against other tools. This helps in understanding performance improvements and variations.

```sh
node benchmarks/compare-tools.js 3 ./benchmarks/test-files
```

--------------------------------

### Common Browserslist Query: Legacy Support

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/browserslist.mdx

A common browserslist query including legacy support for Internet Explorer 11.

```bash
--browserslistQuery="> 0.25%, not dead, IE 11"
```

--------------------------------

### Check ES5 Compatibility

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/quickstart.mdx

Verify that your bundled JavaScript files conform to the ES5 standard. Specify the target ECMAScript version and the file path pattern.

```bash
npx es-check es5 './dist/**/*.js'
```

--------------------------------

### Configuration File for ES Check

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/gettingstarted.mdx

Create a .escheckrc JSON file to define consistent configuration for ES Check, including the target ECMAScript version, files to check, and files to exclude.

```json
{
  "ecmaVersion": "es6",
  "module": false,
  "files": "./dist/**/*.js",
  "not": ["./dist/skip/*.js"],
  "checkFeatures": true
}
```

--------------------------------

### Efficient Glob Patterns for ES Check

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/performance.mdx

Use specific file paths and patterns to improve performance by reducing the scope of file system scanning. Avoid overly broad patterns like './**/*.js' when possible.

```bash
# Good - specific patterns
es-check es5 './dist/**/*.js' './lib/**/*.js'

# Less efficient - overly broad
es-check es5 './**/*.js' --not='node_modules'
```

--------------------------------

### Combine Browser Checking with Feature Checking

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Use --checkBrowser and --checkFeatures together to ensure both browser compatibility and feature adherence to the determined ES version.

```sh
es-check --checkBrowser --checkFeatures ./dist/**/*.js
```

--------------------------------

### Babel Configuration for Target Browsers

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/debugging.mdx

Sets up Babel presets to target modern browsers, including IE 11, for transpilation.

```json
{
  "presets": [
    [
      "@babel/preset-env",
      {
        "targets": {
          "browsers": ["last 2 versions", "ie >= 11"]
        }
      }
    ]
  ]
}
```

--------------------------------

### Verify Build Output with grep

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/debugging.mdx

Uses grep to search for specific ES6 syntax like arrow functions or let/const declarations in the generated JavaScript files.

```bash
# Look at the actual generated code
cat ./dist/app.js | grep "=>"  # Find arrow functions
cat ./dist/app.js | grep "const\|let"  # Find ES6 declarations
```

--------------------------------

### Clone ES Check Repository

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/how-to-contribute.mdx

Clone the ES Check repository from GitHub to your local machine. This is the first step after forking the repository.

```bash
git clone https://github.com/yowainwright/es-check.git
```

--------------------------------

### Basic CLI Usage with Globs

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Basic command-line usage of es-check specifying an ECMAScript version and file globs.

```sh
es-check es6 ./js/*.js
```

--------------------------------

### ES Check Configuration in .escheckrc

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/polyfills.mdx

Configure ES Check settings, including polyfill detection options, directly in a `.escheckrc` JSON file for persistent project settings.

```json
{
  "ecmaVersion": "es2017",
  "files": "./dist/**/*.js",
  "checkFeatures": true,
  "checkForPolyfills": true,
  "ignorePolyfillable": "core-js"
}
```

--------------------------------

### Enable TypeScript Support

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/options.mdx

Enable TypeScript file support with the `--typescript` or `--ts` flag. This experimental feature strips type annotations and checks the resulting JavaScript. Runtime support varies by Node.js and Bun versions.

```bash
es-check es5 './src/**/*.{js,ts}' --typescript
```

--------------------------------

### Use Loose Glob Matching

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Enable loose glob matching to include files that might not strictly adhere to glob patterns.

```sh
es-check es5 './dist/**/*.js' './optional/**/*.js' --looseGlobMatching
```

--------------------------------

### Allow Specific Features

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/features.mdx

Use the --allowList flag to permit specific modern features even when targeting older ES versions. This is useful for features that have well-known polyfills or are safe to use.

```bash
es-check es5 './dist/**/*.js' --checkFeatures --allowList="const,let"
```

--------------------------------

### Backward Compatible Usage with Logger

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/programmatic-api.mdx

Demonstrates how to use `runChecks` with a logger object passed directly, mimicking CLI behavior where `process.exit()` is called on errors.

```javascript
const { runChecks, createLogger } = require("es-check");

async function backwardCompatibleUsage() {
  const configs = [
    {
      ecmaVersion: "es5",
      files: ["dist/**/*.js"],
    },
  ];

  // Old style: passing logger directly (CLI behavior)
  const logger = createLogger();
  await runChecks(configs, logger); // Will call process.exit(1) on error
}
```

--------------------------------

### Enable Zsh Shell Completion

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Add the generated zsh completion script to your .zshrc to enable tab completion.

```sh
# Add to ~/.zshrc
es-check completion zsh > ~/.es-check-completion.zsh
 echo 'source ~/.es-check-completion.zsh' >> ~/.zshrc
```

--------------------------------

### Use Files Option Instead of Arguments

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Specify files to check using the --files flag. Note that using both file arguments and the --files flag is an error.

```sh
es-check es6 --files=./dist/main.js,./dist/utils.js
```

--------------------------------

### Pre-filtering Files with Shell Commands for ES Check

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/performance.mdx

Combine shell commands like 'find' with 'xargs' to pre-filter files before passing them to ES Check. This can be more efficient for complex filtering logic than ES Check's built-in options.

```bash
# Use shell commands to filter first
find ./dist -name "*.js" -not -path "*/vendor/*" | xargs es-check es5
```

--------------------------------

### Specify Files with --files

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/options.mdx

Use the `--files` option as an alternative to positional arguments for specifying the files to be checked.

```bash
es-check es6 --files='./dist/**/*.js'
```

--------------------------------

### Process Files with Balanced Batch Size

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Use a balanced --batchSize, like 50, for a mix of speed and memory efficiency, suitable for medium to large codebases.

```sh
# Process 50 files at a time (balanced approach)
es-check es5 './dist/**/*.js' --batchSize 50
```

--------------------------------

### Fastest ES Check Configuration

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/performance.mdx

Command for maximum speed, using syntax-only checks, silent output, specific files, and unlimited batch processing.

```bash
# Syntax only, silent output, specific files
es-check es5 './dist/bundle.min.js' --silent --batchSize 0
```

--------------------------------

### Check Node Modules Dependencies

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Use this command to check the ES compatibility of packages within your node_modules directory. You can specify a single package or use glob patterns for multiple files.

```sh
npx es-check es5 ./node_modules/some-package/dist/index.js
```

```sh
npx es-check es5 './node_modules/**/*.js'
```

--------------------------------

### Ignore Polyfillable Features by Core-JS

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/polyfills.mdx

Specify a polyfill provider like 'core-js' with `--ignorePolyfillable=core-js` to only skip features polyfillable by that specific library.

```bash
es-check es2017 './dist/**/*.js' --checkFeatures --ignorePolyfillable=core-js
```

--------------------------------

### Verifying Source Map File Existence

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/source-maps.mdx

Check if the source map file (.map) exists alongside the JavaScript file.

```sh
ls dist/*.map
```

--------------------------------

### Babel Source Map Configuration

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/source-maps.mdx

Configure Babel to generate source maps for your JavaScript files.

```json
{
  "sourceMaps": true
}
```

--------------------------------

### Check Browser Compatibility

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Validate JavaScript files against a specified browserslist query using the --browserslistQuery flag. This ensures compatibility with target browsers.

```sh
es-check checkBrowser ./dist/**/*.js --browserslistQuery="last 2 versions"
```

--------------------------------

### ES Check Browser Compatibility

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/performance.mdx

Command to check JavaScript compatibility based on browser targets defined in browserslist.

```bash
es-check --checkBrowser './dist/**/*.js'
```

--------------------------------

### Process Files with Limited Batch Size

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Optimize memory usage in memory-constrained environments by setting a specific --batchSize, such as 10 files at a time.

```sh
# Process 10 files at a time (memory-constrained environments)
es-check es5 './dist/**/*.js' --batchSize 10
```

--------------------------------

### Integrate es-check into Build Script

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/programmatic-api.mdx

Run ES compatibility checks as part of your build process. This snippet demonstrates how to use `runChecks` with a configuration for ES5 compatibility.

```javascript
const { runChecks } = require("es-check");

async function buildWithESCheck() {
  // Your build process
  await buildProject();

  // Check ES compatibility
  const configs = [
    {
      ecmaVersion: "es5",
      files: ["dist/**/*.js"],
      checkFeatures: true,
    },
  ];

  const result = await runChecks(configs);

  if (result.success) {
    console.log("Build successful - ES5 compatible");
  } else {
    console.error("Build failed - ES5 compatibility issues");
    console.error(`Found ${result.errors.length} incompatible files`);
    throw new Error("ES compatibility check failed");
  }
}
```

--------------------------------

### Skip Specific Files or Directories

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Use the --not option to exclude specific files or directories from the check.

```sh
es-check es5 './dist/**/*.js' --not=./dist/vendor,./dist/polyfills
```

--------------------------------

### Webpack Source Map Configuration

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/source-maps.mdx

Configure Webpack to generate source maps for bundled code.

```js
module.exports = {
  devtool: "source-map",
};
```

--------------------------------

### Check Inline Script with ES Check

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/debugging.mdx

Command to check the extracted inline script file for ES2015 compatibility.

```bash
es-check es2015 './tmp/inline-script.js'
```

--------------------------------

### Enable Feature Detection

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/features.mdx

Use the --checkFeatures flag to enable detection of ECMAScript features.

```bash
es-check es5 './dist/**/*.js' --checkFeatures
```

--------------------------------

### Enable Bash Shell Completion

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Add the generated bash completion script to your .bashrc or .bash_profile to enable tab completion.

```sh
# Add to ~/.bashrc or ~/.bash_profile
es-check completion > ~/.es-check-completion.bash
 echo 'source ~/.es-check-completion.bash' >> ~/.bashrc
```

--------------------------------

### Run Checks with a Custom Logger

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/programmatic-api.mdx

Shows how to integrate ES Check into your application by providing a custom logger object to the `runChecks` function for detailed output during the check process.

```javascript
const { runChecks } = require("es-check");

async function checkWithLogger() {
  const configs = [
    {
      ecmaVersion: "es6",
      files: ["src/**/*.js"],
      checkFeatures: true,
    },
  ];

  // Custom logger implementation
  const customLogger = {
    info: (msg) => console.log("[INFO]", msg),
    error: (msg) => console.error("[ERROR]", msg),
    warn: (msg) => console.warn("[WARN]", msg),
    debug: (msg) => console.debug("[DEBUG]", msg),
    isLevelEnabled: (level) => true,
  };

  // Pass logger in an options object
  const result = await runChecks(configs, { logger: customLogger });

  if (!result.success) {
    console.error("Check failed!");
    // Handle errors programmatically
    return { success: false, errors: result.errors };
  }
  return { success: true };
}
```

--------------------------------

### Travis CI Configuration

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/ci-integration.mdx

Travis CI configuration to specify Node.js version and run build and ES version checks.

```yaml
language: node_js
node_js:
  - "20"
script:
  - npm run build
  - npx es-check es5 './dist/**/*.js'
```

--------------------------------

### Common Browserslist Query: Modern Browsers

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/browserslist.mdx

A common browserslist query targeting modern versions of Chrome, Firefox, and Safari.

```bash
--browserslistQuery="last 2 chrome versions, last 2 firefox versions, last 2 safari versions"
```

--------------------------------

### Check for Polyfills in JavaScript Files

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/polyfills.mdx

Use the `--checkForPolyfills` flag to detect polyfilled features that might mask ES version incompatibilities in your JavaScript files.

```bash
es-check es5 './dist/**/*.js' --checkForPolyfills
```

--------------------------------

### Basic ES Check Usage

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/options.mdx

The fundamental structure for running ES Check, specifying the ECMAScript version, target files, and optional flags.

```bash
es-check <ecmaVersion> [files...] [options]
```

--------------------------------

### Enable ES Modules Parsing

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/options.mdx

Use the `--module` flag to enable ES modules parsing mode. This is useful when checking code that utilizes import/export syntax.

```bash
es-check es6 './dist/**/*.js' --module
```

--------------------------------

### TypeScript Source Map Configuration

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/source-maps.mdx

Enable source map generation in your TypeScript project.

```json
{
  "compilerOptions": {
    "sourceMap": true
  }
}
```

--------------------------------

### GitLab CI Configuration

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/ci-integration.mdx

GitLab CI configuration to run ES version checks as part of the test stage.

```yaml
es-check:
  stage: test
  script:
    - npm ci
    - npm run build
    - npx es-check es5 './dist/**/*.js'
  only:
    - merge_requests
    - main
```

--------------------------------

### Configure npm Scripts for ES Check

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/installation.mdx

Add npm scripts to your package.json to easily run ES Check for different ECMAScript versions and module types against your project's JavaScript files.

```json
{
  "scripts": {
    "check:es5": "es-check es5 './dist/**/*.js'",
    "check:es6": "es-check es6 './dist/**/*.js'",
    "check:es-modules": "es-check es6 './dist/**/*.js' --module"
  }
}
```

--------------------------------

### Check Browser Compatibility with Browserslist

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/programmatic-api.mdx

Ensure your code is compatible with a specific set of browsers defined by a browserslist query. This uses `ecmaVersion: "checkBrowser"` to determine the target ES version.

```javascript
const { runChecks } = require("es-check");

async function checkBrowserCompatibility() {
  const configs = [
    {
      ecmaVersion: "checkBrowser",
      files: ["dist/**/*.js"],
      browserslistQuery: "last 2 versions, > 1%",
      checkFeatures: true,
    },
  ];

  const result = await runChecks(configs);

  if (!result.success) {
    console.error("Browser compatibility check failed");
    // Handle errors programmatically
    return { success: false, errors: result.errors };
  }
  // Output depends on logger configuration
  // Silent mode: no output
  // With logger: "ES-Check: Using ES11 based on browserslist configuration"
  return { success: true };
}
```

--------------------------------

### Polyfill Detection

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/features.mdx

Use the --checkForPolyfills flag to enable detection of polyfilled features, which helps avoid false positives. Alternatively, use --ignorePolyfillable to ignore all polyfillable features when polyfills are provided externally.

```bash
es-check es2022 './dist/**/*.js' --checkFeatures --checkForPolyfills
```

```bash
es-check es2017 './dist/**/*.js' --checkFeatures --ignorePolyfillable=core-js
```

--------------------------------

### Display Options for ES Check

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/options.mdx

Control the output verbosity and appearance with options like `--noColor`, `--verbose` (or `-v`), `--quiet`, and `--silent`.

```bash
# Example of verbose output
es-check es6 './dist/**/*.js' --verbose
```

--------------------------------

### ES Check Standard Syntax Check

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/performance.mdx

Standard command for syntax-only checking on multiple JavaScript files.

```bash
es-check es5 './dist/**/*.js'
```

--------------------------------

### Basic Error Format from ES Check

Source: https://github.com/yowainwright/es-check/blob/main/site/src/content/docs/debugging.mdx

Illustrates the standard output format when ES Check encounters a single JavaScript incompatibility.

```bash
✗ ES Check failed!
./dist/app.js
  - error: Arrow function is not supported in ES5
  - line: 42:15
  - code: const sum = (a, b) => a + b;
```

--------------------------------

### ES Check CLI Arguments

Source: https://github.com/yowainwright/es-check/blob/main/README.md

Detailed arguments for the ES Check CLI, including the range of supported ECMAScript versions and the 'files' glob pattern.

```sh
Usage: index [options] [ecmaVersion] [files...]

Arguments:
  ecmaVersion                         ecmaVersion to check files against. Can be: es3, es4, es5, es6/es2015, es7/es2016, es8/es2017, es9/es2018, es10/es2019, es11/es2020, es12/es2021,
                                      es13/es2022, es14/es2023, es15/es2024, es16/es2025
  files                               a glob of files to to test the EcmaScript version against
```