concat (Lodash compatible)

Use spread operator or Array#concat instead

This concat function operates inefficiently due to the complex way Lodash handles array concatenation.

Use the more intuitive and modern spread operator [...arr1, ...arr2] or arr1.concat(arr2) instead.

Concatenates multiple arrays and values into a single array.

const result = concat(...values);

Reference

concat(...values)

Use concat when you want to concatenate multiple values and arrays in order to create a new array. Arrays are flattened, and individual values are added as is.

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

// Concatenate individual values
concat(1, 2, 3);
// Returns: [1, 2, 3]

// Concatenate arrays
concat([1, 2], [3, 4]);
// Returns: [1, 2, 3, 4]

// Concatenate values and arrays together
concat(1, [2, 3], 4);
// Returns: [1, 2, 3, 4]

Nested arrays are flattened only one level deep.

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

// Nested arrays are flattened only one level
concat([1, [2, 3]], 4);
// Returns: [1, [2, 3], 4]

// More deeply nested arrays
concat([1, [2, [3, 4]]], 5);
// Returns: [1, [2, [3, 4]], 5]

Handles empty arrays and empty values.

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

// With empty arrays
concat([], [1, 2], [], [3]);
// Returns: [1, 2, 3]

// When no values are provided
concat();
// Returns: []

Parameters

• values (...(T | readonly T[])): Values and arrays to concatenate. Each array is flattened one level.

Returns

(T[]): Returns a new array with all values and array elements concatenated in order.