Lodash _.isSymbol() Method

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

Definition

Checks if value is classified as a Symbol primitive or Symbol object. Part of Lodash Lang since 4.0.0 (stable — not deprecated).

Note: Needs an ES2015+ runtime with Symbol. Well-known symbols like Symbol.iterator are real Symbols.

Syntax

Call _.isSymbol. Start with this line.

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

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

Library declarations
Lodash
_.isSymbol(value)

Parameters

ParameterDescription
valueRequired. The value to check

Return Value

Return ValueDescription
*true if Symbol, else false

Lodash Examples

Example 1 — Official: Symbol.iterator

Well-known symbols are real Symbol primitives.

Lodash
_.isSymbol(Symbol.iterator);
// → true
Try It Yourself

How It Works

  1. Well-known. Symbol.iterator is a built-in Symbol.
  2. Type. typeof Symbol.iterator === "symbol".
  3. Result. Returns true.
  4. Use. Detect protocol keys before calling iterable APIs.

Example 2 — Official: String 'abc'

Ordinary text is not a Symbol.

Lodash
_.isSymbol('abc');
// → false
Try It Yourself

How It Works

  1. Input. Official sample: the string 'abc'.
  2. Wrong type. It is text, not a Symbol.
  3. Result. Returns false.
  4. Related. Use _.isString for strings.

Example 3 — Custom Symbol('id')

User-created Symbols pass the same way.

Lodash
var id = Symbol('id');

_.isSymbol(id);
// → true

Symbol('id') === Symbol('id');
// → false   // each call is unique
Try It Yourself

How It Works

  1. Create. Symbol('id') makes a new primitive.
  2. isSymbol. Classifies it as Symbol → true.
  3. Unique. Two calls with the same label are still different Symbols.
  4. Registry. Use Symbol.for when you need a shared global Symbol.

Example 4 — Boxed Symbol Object

Lodash also accepts Object(sym); typeof alone does not.

Lodash
var boxed = Object(Symbol('x'));

_.isSymbol(boxed);           // → true
typeof boxed === "symbol";   // → false  (typeof is "object")
Try It Yourself

How It Works

  1. Boxed. Object(Symbol(...)) wraps a Symbol.
  2. isSymbol. Sees the Symbol brand → true.
  3. typeof. Reports "object" → fails a naive check.
  4. Prefer. Use Symbol primitives in new code.

Example 5 — Common Non-Symbols

Values that often appear near keys but are not Symbols.

Lodash
_.isSymbol(null);   // → false
_.isSymbol(1);      // → false
_.isSymbol({});     // → false
_.isSymbol('sym');  // → false
Try It Yourself

How It Works

  1. nullish / number. Wrong types → false.
  2. Object. Plain {} is not a Symbol.
  3. String label. 'sym' is text, not Symbol('sym').
  4. Rule. Only Symbol-branded values pass.
Compatibility

Browser & Runtime Support

_.isSymbol is a Lodash Lang helper since 4.0.0. It runs anywhere Lodash runs on an ES2015+ engine with Symbol — modern browsers (CDN or bundle) and Node.js / Bun / Deno with npm install lodash.

✓ Stable · Lodash 4.0.0+

_.isSymbol()

Available in [email protected] full builds and the lodash/isSymbol modular import. Requires a runtime that provides the Symbol built-in (all modern engines).

100% With Lodash 4.x + Symbol
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
_.isSymbol Lodash 4.0.0+

Bottom line: Safe for production once Lodash is loaded on an ES2015+ runtime. Prefer import isSymbol from "lodash/isSymbol" for smaller bundles. For primitives only, typeof value === "symbol" is enough.

Frequently Asked Questions

_.isSymbol(value) returns true if value is a Symbol primitive or a boxed Symbol object. Strings, numbers, null, and plain objects return false.
Yes. Well-known symbols like Symbol.iterator are real Symbol primitives — _.isSymbol(Symbol.iterator) is true.
Yes. Lodash also accepts boxed Symbol objects. typeof alone reports "object" for those wrappers.
typeof only catches primitives. _.isSymbol also accepts rare Object(sym) wrappers via the [object Symbol] brand.
No. Symbol('x') !== Symbol('x'). Each call creates a new unique Symbol; the description is only for debugging.
Use import isSymbol from "lodash/isSymbol" or require("lodash/isSymbol"). Full build: import _ from "lodash" then _.isSymbol.

Next: _.isTypedArray()

Check whether a value is a typed array (Uint8Array, Float64Array, …).

_.isTypedArray() 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
  • 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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