### Get a Key-Value Pair

Source: https://deno.land/manual/runtime/kv

Retrieve a value from Deno KV using `kv.get()`. The returned `KvEntry` object contains the key, value, and versionstamp.

```APIDOC
## kv.get()

### Description
Retrieves a single key-value pair from the Deno KV database.

### Method
`kv.get(key: readonly (string | number | boolean | bigint | null)[]): Promise<Deno.KvEntry | null>`

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
- **key** (Array) - Required - An array representing the key to retrieve.

### Request Example
```javascript
const kv = await Deno.openKv();
const entry = await kv.get(["preferences", "ada"]);
console.log(entry.key);
console.log(entry.value);
console.log(entry.versionstamp);
```

### Response
#### Success Response (200)
Returns a `KvEntry` object containing the key, value, and versionstamp, or `null` if the key does not exist.

#### Response Example
```json
{
  "key": ["preferences", "ada"],
  "value": {
    "username": "ada",
    "theme": "dark",
    "language": "en-US"
  },
  "versionstamp": "00000000000000010000"
}
```
```

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

### Set and Get Display Name in Deno KV

Source: https://deno.land/manual/runtime/kv

Helper functions to set and retrieve user display names from Deno KV. Uses a persistent store by default.

```typescript
async function setDisplayName(
  kv: Deno.Kv,
  username: string,
  displayname: string,
) {
  await kv.set(["preferences", username, "displayname"], displayname);
}

async function getDisplayName(
  kv: Deno.Kv,
  username: string,
): Promise<string | null> {
  return (await kv.get(["preferences", username, "displayname"]))
    .value as string;
}

```

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

### Secondary Indexes: Get by Username

Source: https://deno.land/manual/runtime/kv

Retrieve user preferences using the primary key (username). This function demonstrates a direct lookup using the username.

```typescript
async function getByUsername(username) {
  // Use as before...
  const r = await kv.get(["preferences", username]);
  return r;
}

```

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

### Get a Key-Value Pair from Deno KV

Source: https://deno.land/manual/runtime/kv

Retrieve a stored key-value pair using `kv.get()`. The returned `KvEntry` object contains the key, value, and versionstamp. The versionstamp is used to track updates.

```typescript
const entry = await kv.get(["preferences", "ada"]);
console.log(entry.key);
console.log(entry.value);
console.log(entry.versionstamp);
```

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

### Get Multiple Key-Value Pairs in Deno KV

Source: https://deno.land/manual/runtime/kv

Efficiently retrieve multiple key-value pairs by passing an array of keys to `kv.getMany()`. If a key does not exist, its corresponding value and versionstamp in the result will be `null`.

```typescript
const kv = await Deno.openKv();
const result = await kv.getMany([
  ["preferences", "ada"],
  ["preferences", "grace"],
]);
result[0].key; // ["preferences", "ada"]
result[0].value; // { ... }
result[0].versionstamp; // "00000000000000010000"
result[1].key; // ["preferences", "grace"]
result[1].value; // null
result[1].versionstamp; // null
```

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

### Get Multiple Key-Value Pairs

Source: https://deno.land/manual/runtime/kv

Efficiently retrieve multiple key-value pairs using `kv.getMany()`. It returns an array of `KvEntry` objects, where values or versionstamps can be `null` if a key is not found.

```APIDOC
## kv.getMany()

### Description
Retrieves multiple key-value pairs from the Deno KV database.

### Method
`kv.getMany(keys: readonly (readonly (string | number | boolean | bigint | null)[])[]): Promise<Array<Deno.KvEntry | null>>`

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
- **keys** (Array of Arrays) - Required - An array of keys to retrieve.

### Request Example
```javascript
const kv = await Deno.openKv();
const result = await kv.getMany([
  ["preferences", "ada"],
  ["preferences", "grace"],
]);
console.log(result[0].key);
console.log(result[0].value);
console.log(result[1].value);
```

### Response
#### Success Response (200)
Returns an array of `KvEntry` objects or `null` for each requested key.

#### Response Example
```json
[
  {
    "key": ["preferences", "ada"],
    "value": {
      "username": "ada",
      "theme": "dark",
      "language": "en-US"
    },
    "versionstamp": "00000000000000010000"
  },
  null
]
```
```

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

### Secondary Indexes: Get by Email

Source: https://deno.land/manual/runtime/kv

Retrieve user preferences using a secondary index (email). This function first looks up the primary key using the email address and then performs a second lookup to retrieve the actual preference data.

```typescript
async function getByEmail(email) {
  // Look up the key by email, then second lookup for actual data
  const r1 = await kv.get(["preferencesByEmail", email]);
  const r2 = await kv.get(r1.value);
  return r2;
}

```

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

### Atomic Transaction: Conditional Insert

Source: https://deno.land/manual/runtime/kv

Execute atomic transactions to conditionally perform operations. This example creates a new preferences object only if it doesn't already exist, using `null` versionstamps to check for absence.

```typescript
const kv = await Deno.openKv();

const key = ["preferences", "alan"];
const value = {
  username: "alan",
  theme: "light",
  language: "en-GB",
};

const res = await kv.atomic()
  .check({ key, versionstamp: null }) // `null` versionstamps mean 'no value'
  .set(key, value)
  .commit();
if (res.ok) {
  console.log("Preferences did not yet exist. Inserted!");
} else {
  console.error("Preferences already exist.");
}

```

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

### Test Deno KV with In-Memory Datastore

Source: https://deno.land/manual/runtime/kv

Use `Deno.openKv(':memory:')` to create an ephemeral Deno KV datastore for testing. This ensures tests are repeatable and isolated.

```typescript
Deno.test("Preferences", async (t) => {
  const kv = await Deno.openKv(":memory:");

  await t.step("can set displayname", async () => {
    let displayName = await getDisplayName(kv, "example");
    assertEquals(displayName, null);

    await setDisplayName(kv, "example", "Exemplary User");

    displayName = await getDisplayName(kv, "example");
    assertEquals(displayName, "Exemplary User");
  });
});

```

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

### List Key-Value Pairs by Prefix

Source: https://deno.land/manual/runtime/kv

Use `kv.list()` to retrieve all key-value pairs that share a common prefix. The results are ordered lexicographically.

```APIDOC
## kv.list()

### Description
Retrieves a stream of key-value pairs from the Deno KV database that match a given prefix.

### Method
`kv.list(options?: { prefix?: readonly (string | number | boolean | bigint | null)[]; limit?: number; reverse?: boolean; }): AsyncIterableIterator<Deno.KvEntry>

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
- **options** (Object) - Optional - Configuration for the list operation.
  - **prefix** (Array) - Optional - The prefix to filter keys by.
  - **limit** (number) - Optional - The maximum number of entries to return.
  - **reverse** (boolean) - Optional - If true, returns entries in reverse lexicographical order.

### Request Example
```javascript
const kv = await Deno.openKv();
const entries = kv.list({ prefix: ["preferences"] });
for await (const entry of entries) {
  console.log(entry.key);
  console.log(entry.value);
}
```

### Response
#### Success Response (200)
Returns an `AsyncIterableIterator` that yields `KvEntry` objects matching the prefix.

#### Response Example
```json
[
  {
    "key": ["preferences", "ada"],
    "value": {
      "username": "ada",
      "theme": "dark",
      "language": "en-US"
    },
    "versionstamp": "00000000000000010000"
  }
]
```
```

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

### Open and Close Deno KV Database

Source: https://deno.land/manual/runtime/kv

Obtain a reference to the KV database and close the connection when done. Pass an optional path to specify the database file location.

```typescript
const kv = await Deno.openKv();
// Execute some queries ...
kv.close();

```

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

### List Key-Value Pairs with a Prefix in Deno KV

Source: https://deno.land/manual/runtime/kv

Retrieve all key-value pairs that share a common prefix using `kv.list()`. The entries are returned in lexicographical order based on the key components following the prefix.

```typescript
const kv = await Deno.openKv();
const entries = kv.list({ prefix: ["preferences"] });
for await (const entry of entries) {
  console.log(entry.key); // ["preferences", "ada"]
  console.log(entry.value); // { ... }
  console.log(entry.versionstamp); // "00000000000000010000"
}
```

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

### Watch for Deno KV Updates

Source: https://deno.land/manual/runtime/kv

Listen for changes on specified keys and retrieve new values. This is useful for real-time applications like chat.

```typescript
let seen = "";
for await (const [messageId] of kv.watch([["last_message_id", roomId]])) {
  const newMessages = await Array.fromAsync(kv.list({
    start: ["messages", roomId, seen, ""],
    end: ["messages", roomId, messageId, ""],
  }));
  await websocket.write(JSON.stringify(newMessages));
  seen = messageId;
}

```

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

### Secondary Indexes: Save Preferences

Source: https://deno.land/manual/runtime/kv

Implement secondary indexes to access data by multiple keys. This function saves user preferences using a primary key (username) and a secondary key (email), where the secondary index value points to the primary key.

```typescript
const kv = await Deno.openKv();

async function savePreferences(prefs) {
  const key = ["preferences", prefs.username];

  // Set the primary key
  const r = await kv.set(key, prefs);

  // Set the secondary key's value to be the primary key
  await kv.set(["preferencesByEmail", prefs.email], key);

  return r;
}

```

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

### Set a Key-Value Pair in Deno KV

Source: https://deno.land/manual/runtime/kv

Use `kv.set()` to store a JavaScript object as a value associated with a key. Keys can be arrays of strings, numbers, bigints, or booleans. Values can be arbitrary JavaScript objects.

```typescript
const kv = await Deno.openKv();

const prefs = {
  username: "ada",
  theme: "dark",
  language: "en-US",
};

const result = await kv.set(["preferences", "ada"], prefs);
```

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

### Delete a Key-Value Pair

Source: https://deno.land/manual/runtime/kv

Use `kv.delete()` to remove a key from the database. No action is taken if the key does not exist.

```typescript
const kv = await Deno.openKv();
await kv.delete(["preferences", "alan"]);

```

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

### Set a Key-Value Pair

Source: https://deno.land/manual/runtime/kv

Use `kv.set()` to store a JavaScript object as a value for a given key. Keys are arrays of JavaScript types, and values can be arbitrary objects. This method also updates existing entries.

```APIDOC
## kv.set()

### Description
Stores a key-value pair in the Deno KV database. If the key already exists, its value will be updated.

### Method
`kv.set(key: readonly (string | number | boolean | bigint | null)[], value: any): Promise<Deno.KvCommitResult> `

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
- **key** (Array) - Required - An array representing the key. Can contain strings, numbers, bigints, booleans, or null.
- **value** (any) - Required - The JavaScript object to store as the value.

### Request Example
```javascript
const kv = await Deno.openKv();
const prefs = {
  username: "ada",
  theme: "dark",
  language: "en-US",
};
await kv.set(["preferences", "ada"], prefs);
```

### Response
#### Success Response (200)
Returns a `KvCommitResult` object containing information about the commit.

#### Response Example
```json
{
  "versionstamp": "00000000000000010000"
}
```
```

=== COMPLETE CONTENT === This response contains all available snippets from this library. No additional content exists. Do not make further requests.