### Build the Client

Source: https://github.com/getlago/lago-javascript-client/blob/main/README.md

Build the client for distribution using Deno.

```bash
deno task build
```

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

### Run Tests

Source: https://github.com/getlago/lago-javascript-client/blob/main/README.md

Execute the test suite using Deno.

```bash
deno task test
```

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

### Install Lago JavaScript Client with npm

Source: https://github.com/getlago/lago-javascript-client/blob/main/README.md

Install the package via npm before importing it in your project.

```bash
npm install lago-javascript-client
```

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

### Publish to npm

Source: https://github.com/getlago/lago-javascript-client/blob/main/README.md

Build the package and publish it to npm from the npm directory.

```bash
deno task build
cd npm
npm publish
```

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

### Webhook Payload Types - Indexed Lookup by webhook_type

Source: https://github.com/getlago/lago-javascript-client/blob/main/README.md

Use LagoWebhookPayloads to get fully typed webhook payloads by indexing with the webhook_type string, e.g., 'alert.triggered'.

```typescript
import type { LagoWebhookPayloads } from 'lago-javascript-client';

app.post('/webhooks', (req, res) => {
    const event = req.body as LagoWebhookPayloads['alert.triggered'];
    // event.triggered_alert is fully typed
    console.log(event.triggered_alert.external_customer_id);
    res.sendStatus(200);
});
```

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

### Generate Client from OpenAPI

Source: https://github.com/getlago/lago-javascript-client/blob/main/README.md

Run the Deno task to regenerate the client from the OpenAPI document.

```bash
deno task generate:openapi
```

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

### Import and Use Client with Error Handling (npm and Deno)

Source: https://github.com/getlago/lago-javascript-client/blob/main/README.md

Shows how to import the Client and getLagoError utility for npm and Deno, then create a billable metric with error handling. Replace '__YOUR_API_KEY__' with your actual API key.

```typescript
// npm
import { Client, getLagoError } from 'lago-javascript-client';

// Deno
import { Client, getLagoError } from 'https://deno.land/x/lago/mod.ts';

const lagoClient = Client('__YOUR_API_KEY__');

try {
    const { data } = await lagoClient.billableMetrics.createBillableMetric(billableMetric);
} catch (error) {
    const lagoError = await getLagoError<typeof lagoClient.billableMetrics.createBillableMetric>(error);
}
```

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

### Pass Custom Fetch Instance to Lago Client

Source: https://github.com/getlago/lago-javascript-client/blob/main/README.md

For Node.js versions below 18, polyfill the Fetch API and pass a custom fetch instance to the client using the 'customFetch' option.

```typescript
import { Client } from 'lago-javascript-client';
import fetch from 'node-fetch';

const lagoClient = Client("api_key", { customFetch: fetch });
```

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

### Error Handling with getLagoError Utility

Source: https://github.com/getlago/lago-javascript-client/blob/main/README.md

Use the getLagoError<>() utility function to extract the error object and TypeScript type when an API call fails.

```typescript
try {
    const { data } = await lagoClient.billableMetrics.createBillableMetric(billableMetric);
} catch (error) {
    const lagoError = await getLagoError<typeof lagoClient.billableMetrics.createBillableMetric>(error);
}
```

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

### Webhook Payload Types - Discriminated Union Handler

Source: https://github.com/getlago/lago-javascript-client/blob/main/README.md

Use LagoWebhookPayload as a discriminated union to handle multiple webhook events with type narrowing based on webhook_type.

```typescript
import type { LagoWebhookPayload } from 'lago-javascript-client';

function handle(event: LagoWebhookPayload) {
    switch (event.webhook_type) {
        case 'alert.triggered':
            // event.triggered_alert is typed
            return event.triggered_alert;
        case 'invoice.created':
            // event.invoice is typed
            return event.invoice;
        case 'subscription.terminated':
            return event.subscription;
    }
}
```

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