Lodash _.defaultTo() Method

Beginner
5 min read
Updated: Nov 2026
5 examples
Util
Decorative image with the word DEFAULTTO

Definition

Checks value and returns defaultValue when value is NaN, null, or undefined. Part of Lodash Util since 4.14.0 (stable — not deprecated).

Note: Unlike ||, it keeps 0, '', and false. Unlike ??, it also replaces NaN.

Syntax

Call _.defaultTo. Start with this line.

Lodash
_.defaultTo(value, defaultValue)
CallWhat it does
_.defaultTo(value, defaultValue)Primary signature.
_.defaultTo(...)Call the util helper.

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

Library declarations
Lodash
_.defaultTo(value, defaultValue)

Parameters

ParameterDescription
valueRequired. Value to check
defaultValueRequired. Returned when value is null, undefined, or NaN

Return Value

Return ValueDescription
*Resolved value (original or default)

Lodash Examples

Example 1 — Official: Keep Value or Use Default

Pass a present value, then an absent one.

Lodash
_.defaultTo(1, 10);
// → 1

_.defaultTo(undefined, 10);
// → 10
Try It Yourself

How It Works

  1. Present. 1 is fine → return 1.
  2. Missing. undefined triggers the default.
  3. Result. Second call yields 10.
  4. Pattern. Same idea for API fields that may be absent.

Example 2 — null Fallback

null is treated like a missing value.

Lodash
_.defaultTo(null, "Guest");
// → "Guest"

_.defaultTo("Ada", "Guest");
// → "Ada"
Try It Yourself

How It Works

  1. null check. null == null → use default.
  2. Fallback. Returns "Guest".
  3. Real name. "Ada" is kept.
  4. Use. Typical display-name or label defaulting.

Example 3 — Keep 0 and ''

Falsy-but-valid values are not replaced.

Lodash
_.defaultTo(0, 10);
// → 0

_.defaultTo("", "n/a");
// → ""
Try It Yourself

How It Works

  1. Zero. 0 is neither nullish nor NaN → kept.
  2. Empty string. Same rule → kept.
  3. Why it matters. Counts and blank text stay meaningful.
  4. vs ||. 0 || 10 would wrongly become 10.

Example 4 — NaN Gets the Default

Lodash also treats NaN as a trigger (unlike ??).

Lodash
_.defaultTo(NaN, 10);
// → 10

_.defaultTo(Number("oops"), 0);
// → 0
Try It Yourself

How It Works

  1. NaN test. Internally uses value !== value.
  2. Fallback. NaN → 10.
  3. Parse fail. Number("oops") is NaN → 0.
  4. vs ??. NaN ?? 10 stays NaN; Lodash replaces it.

Example 5 — defaultTo vs ||

See how || over-replaces valid zeros.

Lodash
_.defaultTo(0, 10);
// → 0

0 || 10;
// → 10

_.defaultTo(null, 10);
// → 10

null || 10;
// → 10
Try It Yourself

How It Works

  1. defaultTo + 0. Keeps a real zero.
  2. || + 0. Treats zero as falsy → 10.
  3. null. Both helpers fall back to 10.
  4. Choose. Prefer defaultTo (or ??) when 0 is valid.
Compatibility

Browser & Runtime Support

_.defaultTo is a Lodash Util helper since 4.14.0. It runs anywhere Lodash 4.14+ runs — modern browsers (CDN or bundle) and Node.js / Bun / Deno with npm install lodash.

✓ Stable · Lodash 4.14.0+

_.defaultTo()

Available in [email protected] full builds and the lodash/defaultTo modular import. Works in evergreen browsers and current Node LTS when Lodash ≥ 4.14 is installed.

100% With Lodash 4.14+
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
_.defaultTo Lodash 4.14.0+

Bottom line: Safe for production once Lodash 4.14+ is loaded. Prefer import defaultTo from "lodash/defaultTo" for smaller bundles. Use it when 0 and empty strings must survive, but NaN should still fall back.

Frequently Asked Questions

_.defaultTo(value, defaultValue) returns value unless value is null, undefined, or NaN — then it returns defaultValue. Official: _.defaultTo(1, 10) → 1; _.defaultTo(undefined, 10) → 10.
No. 0, '', and false are kept. Only null, undefined, and NaN trigger the fallback.
|| replaces every falsy value (0, '', false, null, undefined, NaN). _.defaultTo keeps 0 and '' — safer for counts and text fields.
?? falls back only for null and undefined. _.defaultTo also falls back for NaN. That NaN check is the main Lodash difference.
_.defaultTo works on one value. _.defaults fills missing undefined keys on an object from source objects.
Use import defaultTo from "lodash/defaultTo" or require("lodash/defaultTo"). Full build: import _ from "lodash" then _.defaultTo.

Next: _.flow()

Compose functions left-to-right into one pipeline.

_.flow() 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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