Many methods provided by utility libraries like Lodash and Underscore.js have native equivalents in modern JavaScript environments (ES6 and later).

Why is this an issue?

Using native methods reduces the dependency on external libraries, decreases the bundle size of an application, and often improves performance because JavaScript engines heavily optimize built-in APIs.

When the standard API already covers the same use case, keeping the Lodash or Underscore.js call adds unnecessary indirection. Readers must translate a library-specific helper into a platform feature they already know, and the project keeps a dependency for behavior that the runtime already exposes.

Instead of importing and using lodash or underscore methods, prefer the native standard libraries unless the code specifically relies on the extra edge-case handling or null-safety the external library provides.

What is the potential impact?

Using utility wrappers when the platform already provides the same behavior makes code less idiomatic and harder to maintain. It also keeps an unnecessary dependency surface in the codebase.

How to fix it

Replace the library call with the standard API that matches the current behavior. This rule only recommends alternatives that are available for the configured ECMAScript version.

Code examples

Noncompliant code example

import _ from "lodash";

const uniqueIds = _.uniq(ids); // Noncompliant
const isList = _.isArray(value); // Noncompliant

Compliant solution

const uniqueIds = [...new Set(ids)]; // Compliant
const isList = Array.isArray(value); // Compliant

Pitfalls

Do not assume that every Lodash or Underscore.js helper maps directly to the same standard API.

• Many Lodash and Underscore.js helpers tolerate null and undefined, while native APIs such as Object.keys() and Array.prototype.slice() throw for those values.
• Collection helpers can accept plain objects and shorthand predicates, while native array methods require an array-like receiver and an explicit callback. This rule is intentionally conservative and only reports collection helpers when the receiver shape and callback make the native call a close match.
• If preserving the existing behavior requires extra guards, coercion, or an object-to-array conversion, keep the library helper or refactor the surrounding code deliberately instead of applying a blind replacement.

Resources

Documentation

• You Might Not Need Lodash - Overview of native alternatives to Lodash helpers
• Lodash Documentation - Lodash API reference
• Underscore.js Documentation - Underscore.js API reference
• MDN Documentation - Object - Object built-ins and static methods
• MDN Documentation - Array - Array methods and constructors