Lodash Lang methods

Beginner

⏱️ 12 min read

📚 Updated: May 2026

🎯 2 Code examples

Lodash

What you’ll learn

Which Lang helpers solve type-checking and conversion tasks quickly.
How to choose between isNil, isEmpty, and stricter validators.
When to use deep comparison with isEqual versus native equality operators.
How to install and import Lodash in a bundle-friendly way.
Where to find each _.methodName in the official Lodash docs.

Prerequisites

JavaScript primitives, objects, and equality basics. This page focuses on the value-shape edge cases many native checks miss.

Core types: primitive values, objects, arrays, functions, and nullish values in JavaScript.
Equality operators: difference between ==, ===, and reference equality for objects.
Imports: ESM or CommonJS module usage so examples map directly to your runtime.

Overview

Lodash Lang methods are a toolbox for value introspection. They help you avoid brittle checks, normalize unknown input shapes, and compare nested data safely.

Type guards

Use checks like isArray, isPlainObject, and isFunction before branching into strict processing logic.

Deep equality & matching

isEqual and isMatch reduce boilerplate when comparing nested API payloads and config objects.

Conversions

Methods like toNumber, toInteger, and toArray make incoming values predictable before calculations.

Install and import

Install Lodash once, then import only what you need to keep bundle size under control.

Terminal

npm install lodash

javascript

import isNil from "lodash/isNil";
import isEqual from "lodash/isEqual";
import toNumber from "lodash/toNumber";

const payload = { retries: "3", tag: null };

const retries = toNumber(payload.retries); // 3
const missingTag = isNil(payload.tag); // true
const same = isEqual({ a: [1, 2] }, { a: [1, 2] }); // true

🔄 Common usage patterns

Most Lang helpers fall into one of these patterns. Picking the right group first keeps code readable and avoids over-checking.

Goal	Typical methods	When useful
Guard runtime inputs	`isArray`, `isObject`, `isString`	Before parsing request bodies or third-party SDK responses.
Handle nullish safely	`isNil`, `isUndefined`, `isNull`	When optional values are valid but missing keys need separate logic.
Compare nested values	`isEqual`, `isMatch`	In tests, cache invalidation, and settings diffing.
Normalize data	`toNumber`, `toInteger`, `toArray`, `castArray`	Before arithmetic, loops, or schema validation.
Copy values	`clone`, `cloneDeep`	When isolation is required before mutating derived objects.

Method index

Each method links to its Lodash 4.x documentation entry.

Method	What it does
`_.castArray()`	Wrap a value in an array unless it is already an array.
`_.clone()`	Create a shallow clone of a value.
`_.cloneDeep()`	Create a deep clone of a value recursively.
`_.cloneDeepWith()`	Deep clone with a customizer for special cases.
`_.cloneWith()`	Shallow clone with a customizer override.
`_.conformsTo()`	Check if an object conforms to source predicates.
`_.eq()`	Compare two values with SameValueZero semantics.
`_.gt()`	Check if first value is greater than second.
`_.gte()`	Check if first value is greater than or equal to second.
`_.isArguments()`	Check if a value is likely an arguments object.
`_.isArray()`	Check if a value is an array.
`_.isArrayBuffer()`	Check if a value is an ArrayBuffer.
`_.isArrayLike()`	Check if a value is array-like (has length, not a function).
`_.isArrayLikeObject()`	Check if value is object-like and array-like.
`_.isBoolean()`	Check if a value is classified as a boolean.
`_.isBuffer()`	Check if a value is a Node.js Buffer.
`_.isDate()`	Check if a value is a Date object.
`_.isElement()`	Check if a value is likely a DOM element.
`_.isEmpty()`	Check if a collection, map, set, or object is empty.
`_.isEqual()`	Perform a deep equality comparison.
`_.isEqualWith()`	Deep equality comparison with a customizer.
`_.isError()`	Check if a value is an Error object.
`_.isFinite()`	Check if a value is a finite primitive number.
`_.isFunction()`	Check if a value is classified as a function.
`_.isInteger()`	Check if a value is an integer.
`_.isLength()`	Check if a value is a valid array-like length.
`_.isMap()`	Check if a value is a Map object.
`_.isMatch()`	Check if object partially matches source properties.
`_.isMatchWith()`	Partial match check with a customizer.
`_.isNaN()`	Check if value is NaN (number only).
`_.isNative()`	Check if a value appears to be a native function.
`_.isNil()`	Check if value is null or undefined.
`_.isNull()`	Check if value is null.
`_.isNumber()`	Check if a value is classified as a number.
`_.isObject()`	Check if value is the language type of Object.
`_.isObjectLike()`	Check if value is object-like (not null, typeof object).
`_.isPlainObject()`	Check if value is a plain object.
`_.isRegExp()`	Check if value is a RegExp object.
`_.isSafeInteger()`	Check if value is a safe integer.
`_.isSet()`	Check if value is a Set object.
`_.isString()`	Check if value is a string.
`_.isSymbol()`	Check if value is a symbol.
`_.isTypedArray()`	Check if value is a typed array.
`_.isUndefined()`	Check if value is undefined.
`_.isWeakMap()`	Check if value is a WeakMap object.
`_.isWeakSet()`	Check if value is a WeakSet object.
`_.lt()`	Check if first value is less than second.
`_.lte()`	Check if first value is less than or equal to second.
`_.toArray()`	Convert a value to an array.
`_.toFinite()`	Convert value to a finite number.
`_.toInteger()`	Convert value to an integer.
`_.toLength()`	Convert value to a valid length.
`_.toNumber()`	Convert value to a number.
`_.toPlainObject()`	Convert value to a plain object with inherited props.
`_.toSafeInteger()`	Convert value to a safe integer.
`_.toString()`	Convert value to a string.

Pitfalls to avoid

Overuse

Checking everything twice

Too many guards can hide assumptions. Validate once at boundaries, then trust typed data internally.

Performance

Unnecessary deep clones

cloneDeep is powerful but expensive on large trees. Use shallow copies when deep isolation is not required.

Equality

Using JSON stringify as comparator

String-based comparisons can fail due to key order and unsupported values; prefer isEqual for robust deep comparisons.

❓ FAQ

What is the Lodash Lang category?

It contains language-level helpers for inspecting values, comparing deeply, cloning safely, and converting unknown inputs to predictable primitives.

When should I use Lodash type checks over native JavaScript?

Use them when inputs may be mixed across runtime boundaries or when edge-case behavior (like typed arrays, maps, or nullish checks) should be explicit and consistent.

What is the difference between isNil, isNull, and isUndefined?

isNil matches null or undefined. isNull only matches null. isUndefined only matches undefined.

Is cloneDeep always safe for performance?

No. Deep cloning can be expensive on large graphs. Prefer shallow clones unless mutation isolation really requires full deep copies.

Summary

Scope: Lodash Lang methods cover type checks, deep equality, cloning, and safe conversions.
Practice: validate at boundaries, then convert data into stable internal shapes.
Next step: start with Lodash _.castArray() Docs or scan the method index above.

Did you know?

Lodash isNil returns true only for null and undefined, which makes it stricter than a generic falsy check.

About the author

Mari Selvan M P 🔗

Developer, cloud engineer, and technical writer

Experience 12 years building web and cloud systems
Focus Full Stack Development, AWS, and Developer Education

I write practical tutorials so students and working developers can learn by doing—from databases and APIs to deployment on AWS.

AWS Certified Developer – Associate (Credly)

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Lodash Function Methods Lodash _.castArray() Docs