JSON.ARRAPPEND

Append values to a JSON array

Appends one or more values to the end of a JSON array at the specified path.

Usage

const newLength = await redis.json.arrappend("user:123", "$.tags", "premium", "verified");

Arguments

key · string · required

The key containing the JSON document

path · string · required

JSONPath expression pointing to the array to append to

values · ...TData[] · required

One or more values to append to the array. Can be any JSON-serializable values.

Response

result · (number | null)[]

An array of numbers representing the new length of the array at each matching path. Returns null for paths that don’t exist or aren’t arrays.

Examples

Append single value to array

// Initial: { "tags": ["developer", "admin"] }
const newLength = await redis.json.arrappend("user:123", "$.tags", "premium");
console.log(newLength); // [3]

// Result: { "tags": ["developer", "admin", "premium"] }

Append multiple values

const newLength = await redis.json.arrappend(
  "user:123",
  "$.tags",
  "verified",
  "active",
  "pro"
);
console.log(newLength); // [6]

// Result: { "tags": ["developer", "admin", "premium", "verified", "active", "pro"] }

Append to nested array

interface Order {
  id: string;
  items: string[];
}

const newLength = await redis.json.arrappend(
  "order:456",
  "$.items",
  "item-123"
);
console.log(newLength); // [4]

Append objects to array

interface Product {
  id: string;
  name: string;
  price: number;
}

const newProduct: Product = {
  id: "prod-789",
  name: "Widget",
  price: 29.99
};

const newLength = await redis.json.arrappend(
  "cart:123",
  "$.products",
  newProduct
);

Append to multiple arrays (wildcard path)

// Initial: {
//   "users": [
//     { "id": 1, "tags": ["active"] },
//     { "id": 2, "tags": ["inactive"] }
//   ]
// }

const newLengths = await redis.json.arrappend(
  "data:1",
  "$.users[*].tags",
  "updated"
);
console.log(newLengths); // [2, 2]

// Result: Both users now have "updated" tag appended

Handle non-existent paths

const newLength = await redis.json.arrappend(
  "user:123",
  "$.nonexistent",
  "value"
);
console.log(newLength); // [null]

JSONPath Syntax

• $.array - Append to a top-level array
• $.nested.array - Append to a nested array
• $.array[0].items - Append to array within array element
• $..array - Append to all matching arrays recursively
• $.items[*].tags - Append to arrays within each item

Notes

• The path must point to an existing array. If the path doesn’t exist or points to a non-array value, null is returned for that path.
• When using wildcard paths, the operation is performed on all matching arrays.
• Values are automatically JSON-serialized before appending.

See Also

• JSON.ARRINDEX - Find index of value in array
• JSON.SET - Set JSON values
• Redis JSON.ARRAPPEND documentation