lodash

4.18.1 · active · verified Sat Apr 18

lodash is a JavaScript utility library providing consistent, cross-environment, performance-optimized, and modular utilities for common programming tasks. It simplifies working with arrays, objects, numbers, strings, and functions, offering a wide range of helpers for iteration, manipulation, and type checking. The current stable version is 4.18.1, with frequent updates for bug fixes and security patches, typically released as minor or patch versions.

Common errors

```
ReferenceError: <variable name> is not defined
```
cause Internal dependency mapping issue in `_.template` or `_.fromPairs` functions when imported individually or from modular builds in versions prior to 4.18.1.

fix Upgrade `lodash` to version `4.18.1` or higher.
```
TypeError: require is not a function
```
cause Attempting to use CommonJS `require` syntax within an ES Module (ESM) file context.

fix Refactor `const _ = require('lodash');` to `import _ from 'lodash';` for ESM compatibility.
```
SyntaxError: Cannot use import statement outside a module
```
cause Attempting to use ES Module `import` syntax within a CommonJS (CJS) file context or a project not configured for ESM.

fix Refactor `import _ from 'lodash';` to `const _ = require('lodash');` for CJS compatibility, or configure your project to use ES Modules (e.g., by setting `"type": "module"` in `package.json`).

Warnings

breaking lodash v4.0.0 introduced significant back-compatible breaking changes to align with semantic versioning practices.
Fix: Consult the [v4.0.0 Changelog](https://github.com/lodash/lodash/wiki/Changelog#v400) for migration details.
breaking lodash v3.0.0 included several back-compatible breaking changes as part of a major cleanup and refactoring.
Fix: Consult the [v3.0.0 release notes](https://github.com/lodash/lodash/tree/3.0.0) for migration details.
gotcha A prototype pollution vulnerability via `_.unset` and `_.omit` path traversal was fixed.
Fix: Upgrade to `lodash@4.18.0` or higher to address security vulnerability GHSA-f23m-r3pf-42rh.
gotcha A `ReferenceError` could occur when using `_.template` or `_.fromPairs` from modular builds due to internal dependency issues.
Fix: Upgrade to `lodash@4.18.1` or higher to resolve this `ReferenceError`.
gotcha Lodash functionality in the Node.js REPL may be inconsistent or require a polyfill for Node.js versions prior to 6.
Fix: Install `n_` (`npm i -g n_`) for Node.js < 6 REPL support, or use Node.js v6 or higher.

Install

npm install lodash npm
yarn add lodash yarn
pnpm add lodash pnpm

Imports

_
wrong:
```
const _ = require('lodash');
```
correct:
```
import _ from 'lodash';
```
The 'lodash' package supports both CommonJS and ESM imports. For optimal tree-shaking in modern bundlers, consider using 'lodash-es'.

Quickstart

Demonstrates importing the full lodash library and using the `_.filter` method to process an array of objects.

import _ from 'lodash';

const users = [
  { 'user': 'barney', 'age': 36, 'active': true },
  { 'user': 'fred',   'age': 40, 'active': false }
];

const activeUsers = _.filter(users, function(o) { return o.active; });

console.log(activeUsers);
// Expected output: [ { user: 'barney', age: 36, active: true } ]

view raw JSON →