Lodash _.isNumber() Method

Beginner
5 min read
Updated: Nov 2026
5 examples
Lang
Decorative image with the word ISNUMBER

Definition

Checks if value is classified as a Number primitive or object. Part of Lodash Lang (stable — not deprecated). Note: Infinity, -Infinity, and NaN count as numbers — use _.isFinite to exclude them.

Pass the value you want to inspect or convert. Read the return type carefully before you use the result.

Syntax

Call _.isNumber. Start with this line.

Lodash
_.isNumber(value)
CallWhat it does
_.isNumber(value)Primary signature.

Prefer import isNumber from "lodash/isNumber" when you want a smaller bundle.

Library declarations
Lodash
_.isNumber(value)

Parameters

ParameterDescription
valueRequired. Value to check

Return Value

Return ValueDescription
*true if classified as a number, else false

Lodash Examples

Example 1 — Official: Numbers, Extremes, Strings

Accept number types; reject numeric-looking strings.

Lodash
console.log(_.isNumber(3));                // true
console.log(_.isNumber(Number.MIN_VALUE)); // true
console.log(_.isNumber(Infinity));         // true
console.log(_.isNumber("3"));              // false
Try It Yourself

How It Works

  1. Literal. 3 is a number primitive → true.
  2. MIN_VALUE. Smallest positive number → still a number.
  3. Infinity. Classified as a number in JavaScript → true.
  4. String. "3" stays a string → false.

Example 2 — NaN Counts as a Number

Type check ≠ “usable for arithmetic.”

Lodash
console.log(_.isNumber(NaN));  // true
console.log(_.isNaN(NaN));     // true
console.log(_.isFinite(NaN));  // false
Try It Yourself

How It Works

  1. Type. typeof NaN === "number" → isNumber is true.
  2. Identity. _.isNaN confirms it is Not-a-Number.
  3. Finite. isFinite rejects NaN for real math.
  4. Pick. Type gate → isNumber; usable value → isFinite.

Example 3 — Numeric Strings Stay Strings

No automatic coercion from text to number.

Lodash
console.log(_.isNumber("3"));          // false
console.log(_.isNumber(Number("3")));  // true
console.log(_.isString("3"));          // true
Try It Yourself

How It Works

  1. Raw string. Looks numeric, typed as string → false.
  2. Coerce. Number("3") becomes a real number → true.
  3. isString. Confirms the original type.
  4. Tip. Parse first when input comes from forms or JSON text.

Example 4 — Boxed Number Objects

Object wrappers still count as numbers for Lodash.

Lodash
console.log(_.isNumber(Object(7))); // true
console.log(typeof Object(7));      // "object"
Try It Yourself

How It Works

  1. Wrapper. Object(7) builds a boxed Number object.
  2. typeof. Reports "object", not "number".
  3. Lodash. Checks the internal brand → still true.
  4. Use. Helps when older APIs return boxed primitives.

Example 5 — isNumber vs isFinite

Type classification versus usable finite math values.

Lodash
console.log(_.isNumber(Infinity)); // true
console.log(_.isFinite(Infinity)); // false

console.log(_.isNumber(42));       // true
console.log(_.isFinite(42));       // true
Try It Yourself

How It Works

  1. Infinity. Still a number type → isNumber is true.
  2. Finite gate. isFinite rejects non-finite values.
  3. Normal value. Both helpers accept 42.
  4. Docs tip. Official note: exclude Infinity / NaN with _.isFinite.
Compatibility

Browser & Runtime Support

_.isNumber is a Lodash Lang helper available in 4.x (and earlier builds). It runs anywhere Lodash runs — modern browsers (via CDN or bundle) and Node.js / Bun / Deno with npm install lodash. Native engines expose related checks via typeof and Number.isFinite, but not this helper by name.

✓ Stable · Lodash 4.x

_.isNumber()

Available in [email protected] full builds and the lodash/isNumber modular import. Works in evergreen browsers and current Node LTS when Lodash is installed.

100% With Lodash 4.x
Google Chrome Supported · Desktop & Mobile
Full support
Mozilla Firefox Supported · Desktop & Mobile
Full support
Apple Safari Supported · macOS & iOS
Full support
Microsoft Edge Supported · Chromium
Full support
Internet Explorer No native support · Use a polyfill
Polyfill
Opera Supported · Modern versions
Full support
Samsung Internet Supported · Android
Full support
Bun Supported · JavaScript runtime
Supported
Deno Supported · JavaScript runtime
Supported
Node.js Supported · Server runtime
Supported
Android WebView Supported · Modern WebView
Full support
_.isNumber Lodash 4.x

Bottom line: Safe for production once Lodash is on the page or in your bundle. Prefer import isNumber from "lodash/isNumber" for smaller builds. Pair with _.isFinite when Infinity/NaN must fail.

Frequently Asked Questions

_.isNumber(value) returns true when value is classified as a Number primitive or a boxed Number object. That includes NaN and ±Infinity.
Yes. Lodash follows ECMAScript typing — typeof NaN and typeof Infinity are both "number". Use _.isFinite when those extremes must be rejected.
Numeric-looking strings stay typeof "string" until you coerce them with Number() or parse functions.
Yes. Object(7) / new Number(7) brand as Number objects, so _.isNumber accepts them.
BigInt is a distinct primitive (typeof "bigint"), so _.isNumber returns false.
Use import isNumber from "lodash/isNumber" or require("lodash/isNumber") so bundlers can tree-shake unused Lodash code. Full build: import _ from "lodash" then _.isNumber.

Next: _.isObject()

Check whether a value is classified as an object.

_.isObject() tutorial →

About the author

Mari Selvan M P
Mari Selvan M P 🔗

Developer, cloud engineer, and technical writer

  • Experience 12 years building web and cloud systems
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I write practical tutorials so students and working developers can learn by doing—from databases and APIs to deployment on AWS.

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