eslint-plugin-lodash

What is eslint-plugin-lodash?

eslint-plugin-lodash is an ESLint plugin that provides linting rules for Lodash, a popular JavaScript utility library. The plugin helps ensure that Lodash is used in an optimal and consistent manner, promoting best practices and preventing common mistakes.

What are eslint-plugin-lodash's main functionalities?

Prefer Lodash methods over native

This rule enforces the use of Lodash methods over native JavaScript methods. It ensures consistency and leverages Lodash's optimizations.

/* eslint lodash/prefer-lodash-method: [2] */
const _ = require('lodash');
const arr = [1, 2, 3];
// Bad: using native method
const doubled = arr.map(x => x * 2);
// Good: using Lodash method
const doubled = _.map(arr, x => x * 2);

Prefer _.get over direct property access

This rule encourages the use of _.get for property access, which is safer and avoids potential errors when accessing deeply nested properties.

/* eslint lodash/prefer-get: [2] */
const _ = require('lodash');
const obj = { a: { b: 2 } };
// Bad: direct property access
const value = obj.a.b;
// Good: using _.get
const value = _.get(obj, 'a.b');

Prefer _.isNil over _.isNull and _.isUndefined

This rule prefers the use of _.isNil, which checks for both null and undefined, over using _.isNull and _.isUndefined separately.

/* eslint lodash/prefer-is-nil: [2] */
const _ = require('lodash');
const value = null;
// Bad: using _.isNull and _.isUndefined
if (_.isNull(value) || _.isUndefined(value)) {
  // do something
}
// Good: using _.isNil
if (_.isNil(value)) {
  // do something
}

Other packages similar to eslint-plugin-lodash

eslint-plugin-underscore

eslint-plugin-underscore is an ESLint plugin that provides linting rules for Underscore.js, another popular JavaScript utility library. It offers similar functionality to eslint-plugin-lodash but is tailored for Underscore.js instead of Lodash.

eslint-plugin-you-dont-need-lodash-underscore

eslint-plugin-you-dont-need-lodash-underscore is an ESLint plugin that helps developers identify places where native JavaScript can be used instead of Lodash or Underscore.js. It promotes the use of native methods over utility libraries, contrasting with eslint-plugin-lodash which encourages the use of Lodash.

README

ESLint-Plugin-Lodash

Lodash-specific linting rules for ESLint.

Installation

Install ESLint either locally or globally.

$ npm install eslint

If you installed ESLint globally, you have to install the Lodash plugin globally too. Otherwise, install it locally.

$ npm install eslint-plugin-lodash

Configuration

Add plugins section and specify ESLint-Plugin-Lodash as a plugin. You can additionally add settings for the plugin.

Shared Rule Settings

These are settings that can be shared by all of the rules. All settings are under the lodash inside the general settings object. For more info about shared settings, read the ESLint Configuration Guide.

• pragma: specifies the name you use for the Lodash variable in your code. Default is _.
• version: specifies the major Lodash Version you are using (default is 4). If you wish to use this plugin with Lodash v3, change this value to 3.

Finally, enable all of the rules that you would like to use.

{
  "plugins": ["lodash"],
  "rules": {
    "lodash/prop-shorthand": 2,
    "lodash/matches-shorthand": [2, "always", 3],
    "lodash/matches-prop-shorthand": [2, "always"],
    "lodash/prefer-chain": [2, 3],
    "lodash/preferred-alias": 2,
    "lodash/no-single-chain": 2,
    "lodash/prefer-reject": [2, 3],
    "lodash/prefer-filter": [2, 3],
    "lodash/callback-binding": 2,
    "lodash/unwrap": 2,
    "lodash/prefer-compact": 2,
    "lodash/no-double-unwrap": 2,
    "lodash/prefer-map": 2,
    "lodash/prefer-wrapper-method": 2,
    "lodash/prefer-invoke-map": 2,
    "lodash/prefer-thru": 2,
    "lodash/prefer-lodash-chain": 2,
    "lodash/prefer-lodash-method": 2,
    "lodash/prefer-lodash-typecheck": 2,
    "lodash/no-commit": 2,
    "lodash/prefer-get": [2, 3],
    "lodash/collection-return": 2,
    "lodash/prefer-matches": [2, 3],
    "lodash/prefer-times": 2,
    "lodash/prefer-startswith": 2,
    "lodash/prefer-noop": 2,
    "lodash/prefer-constant": 2,
    "lodash/chain-style": [2, "as-needed"],
    "lodash/prefer-is-nil": 2,
    "lodash/prefer-over-quantifier": 2
  }
}

Configuration for Using with Lodash v3

Out of the box, this plugin supports the use of Lodash v4. To use with Lodash v3, the config needs to specify the version in the settings, and can't use some rules:

{
  "settings": {
    "lodash": {
      "version": 3
    }
  },
  "rules": {
    "lodash/prop-shorthand": 2,
    "lodash/matches-shorthand": [2, "always", 3],
    "lodash/matches-prop-shorthand": [2, "always"],
    "lodash/prefer-chain": [2, 3],
    "lodash/preferred-alias": 2,
    "lodash/no-single-chain": 2,
    "lodash/prefer-reject": [2, 3],
    "lodash/prefer-filter": [2, 3],
    "lodash/callback-binding": 2,
    "lodash/unwrap": 2,
    "lodash/prefer-compact": 2,
    "lodash/no-double-unwrap": 2,
    "lodash/prefer-map": 2,
    "lodash/prefer-wrapper-method": 2,
    "lodash/prefer-thru": 2,
    "lodash/prefer-lodash-chain": 2,
    "lodash/prefer-lodash-method": 2,
    "lodash/prefer-lodash-typecheck": 2,
    "lodash/no-commit": 2,
    "lodash/prefer-get": [2, 3],
    "lodash/collection-return": 2,
    "lodash/prefer-matches": [2, 3],
    "lodash/prefer-times": 2,
    "lodash/prefer-startswith": 2,
    "lodash/prefer-noop": 2,
    "lodash/prefer-constant": 2,
    "lodash/chain-style": [2, "as-needed"]
  }
}

List of provided rules

Rules are divided into categories for your convenience. All rules are off by default.

Possible Errors

The following rules point out areas where you might have made mistakes.

• callback-binding: Use or avoid thisArg for Lodash method callbacks, depending on major version.
• unwrap: Prevent chaining without evaluation via value() or non-chainable methods like max().,
• no-double-unwrap: Do not use .value() on chains that have already ended (e.g. with max() or reduce())
• collection-return: Always return a value in iteratees of Lodash collection methods that aren't forEach.

Stylistic Issues

These rules are purely matters of style and are quite subjective.

• prop-shorthand: Use/forbid property shorthand syntax.
• matches-prop-shorthand: Prefer matches property shorthand syntax
• matches-shorthand: Prefer matches shorthand syntax
• preferred-alias: Prefer using main method names instead of aliases
• prefer-chain: Prefer a Lodash chain over nested Lodash calls
• no-single-chain: Prevent chaining syntax for single method, e.g. _(x).map().value()
• prefer-reject: Prefer _.reject over filter with !(expression) or x.prop1 !== value
• prefer-filter: Prefer _.filter over _.forEach with an if statement inside.
• prefer-compact: Prefer _.compact over _.filter for only truthy values.
• prefer-map: Prefer _.map over _.forEach with a push inside.
• prefer-wrapper-method: Prefer using array and string methods in the chain and not the initial value, e.g. _(str).split(' ')...
• prefer-invoke-map: Prefer using _.invoke over _.map with a method call inside.
• prefer-thru: Prefer using _.prototype.thru in the chain and not call functions in the initial value, e.g. _(x).thru(f).map(g)...
• no-commit: Do not use .commit() on chains that should end with .value()
• chain-style: Enforce a specific chain style: explicit, implicit, or explicit only when necessary.
• prefer-flat-map Prefer _.flatMap over consecutive map and flatten.

Preference over native

These rules are also stylistic choices, but they also recommend using Lodash instead of native functions and constructs.

• prefer-lodash-chain: Prefer using Lodash chains (e.g. _.map) over native and mixed chains.
• prefer-lodash-method: Prefer using Lodash collection methods (e.g. _.map) over native array methods.
• prefer-lodash-typecheck: Prefer using _.is* methods over typeof and instanceof checks when applicable.
• prefer-get: Prefer using _.get or _.has over expression chains like a && a.b && a.b.c.
• prefer-matches: Prefer _.matches over conditions like a.foo === 1 && a.bar === 2 && a.baz === 3.
• prefer-times: Prefer _.times over _.map without using the iteratee's arguments.
• prefer-startswth: Prefer _.startsWith over a.indexOf(b) === 0.
• prefer-noop: Prefer _.noop over empty functions.
• prefer-constant: Prefer _.constant over functions returning literals.
• prefer-is-nil: Prefer _.isNil over checks for both null and undefined.
• prefer-over-quantifier Prefer _.overSome and _.overEvery instead of checks with && and || for methods that have a boolean check iteratee.

Contributing

Contributions are always welcome! For more info, read our contribution guide.

License

ESLint-plugin-lodash is licensed under the MIT License.