map (Lodash compatibility)

Use Array.prototype.map

This map function operates slowly due to additional features such as handling null or undefined, object iteration, and property extraction. When transforming arrays, JavaScript's built-in Array.prototype.map method is faster and simpler.

Instead, use the faster and more modern Array.prototype.map.

Transforms each element of an array or object to create a new array.

const mapped = map(collection, iteratee);

Reference

map(collection, iteratee)

Use map when you want to transform each element of an array, object, or array-like object. It executes an iteratee function on each element and returns the results as a new array.

import { map } from 'es-toolkit/compat';

// Double each element of an array
map([1, 2, 3], x => x * 2);
// Returns: [2, 4, 6]

// Transform object values
const obj = { a: 1, b: 2 };
map(obj, (value, key) => `${key}:${value}`);
// Returns: ['a:1', 'b:2']

// Extract properties
const users = [
  { name: 'John', age: 30 },
  { name: 'Jane', age: 25 },
];
map(users, 'name');
// Returns: ['John', 'Jane']

null or undefined are treated as empty arrays.

import { map } from 'es-toolkit/compat';

map(null, x => x); // []
map(undefined, x => x); // []

You can extract nested properties by specifying a property path as a string.

import { map } from 'es-toolkit/compat';

const users = [{ info: { name: 'John' } }, { info: { name: 'Jane' } }];
map(users, 'info.name');
// Returns: ['John', 'Jane']

When passing an object, it checks if each element matches that object.

import { map } from 'es-toolkit/compat';

const users = [
  { name: 'John', age: 30 },
  { name: 'Jane', age: 25 },
];
map(users, { age: 30 });
// Returns: [true, false]

Parameters

• collection (T[] | ArrayLike<T> | Record<string, T> | null | undefined): The array or object to iterate over.
• iteratee (function | string | object, optional): The function to execute on each element, a property path, or an object to match. If not provided, returns each element as is.
  • When it's a function, it's called in the form (value, key, collection).
  • When it's a string, it extracts that property.
  • When it's an object, it checks if each element matches the object.

Returns

(U[]): Returns a new array of transformed values.