Lodash _.add() Method

Beginner
5 min read
Updated: Nov 2026
5 examples
Math
Decorative image with the word ADD

Definition

Adds two numbers (augend + addend). Part of Lodash 4.x Math.

Pass the numbers or collection shown below. Check the return value before you chain another math helper.

Syntax

Call _.add. Start with this line.

Lodash
_.add(augend, addend)
CallWhat it does
_.add(augend, addend)Primary signature.
_.add(a, b)Run the math helper on numbers or a collection.

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

Library declarations
Lodash
_.add(augend, addend)

Parameters

ParameterDescription
augendRequired. First number in the addition
addendRequired. Second number in the addition

Return Value

Return ValueDescription
*Sum (or concatenated string)

Lodash Examples

Example 1 — Official: Add Two Numbers

The docs baseline — six plus four.

Lodash
_.add(6, 4);
// → 10
Try It Yourself

How It Works

  1. Inputs. augend = 6, addend = 4.
  2. Numeric path. Both are numbers, so Lodash adds them.
  3. Result. 10.
  4. Use. Same idea as native 6 + 4 for plain numbers.

Example 2 — Undefined Operands

Missing values use additive-identity rules.

Lodash
_.add(undefined, 5);
// → 5

_.add(5, undefined);
// → 5

_.add(undefined, undefined);
// → 0
Try It Yourself

How It Works

  1. One missing. Return the defined operand unchanged.
  2. Both missing. Return 0 (additive identity).
  3. Why. Safe as a _.reduce iteratee when slots may be empty.
  4. Family. Multiply/divide use 1 as their both-undefined default.

Example 3 — String Concatenation

A string operand switches to concat, like native +.

Lodash
_.add(1, "2");
// → "12"

_.add("3", 4);
// → "34"

_.add(_.toNumber("3"), 4);
// → 7
Try It Yourself

How It Works

  1. Detect. Either operand is a string → concat path.
  2. Join. Values become strings and glue together.
  3. Force math. Convert with _.toNumber first.
  4. Tip. Prefer numbers when you mean arithmetic.

Example 4 — Floating-Point Quirk

Lodash does not “fix” IEEE-754 decimals.

Lodash
_.add(0.1, 0.2);
// → 0.30000000000000004

0.1 + 0.2;
// → 0.30000000000000004

_.add(0.1, 0.2) === (0.1 + 0.2);
// → true
Try It Yourself

How It Works

  1. Same math. Uses normal number addition under the hood.
  2. Binary floats. 0.1 and 0.2 are not exact in IEEE-754.
  3. Money. Scale to integer cents or use a decimal library.
  4. Expect. Identical result to native +.

Example 5 — Reduce with _.add

Handy as a two-arg callback for totals.

Lodash
_.reduce([1, 2, 3, 4], _.add);
// → 10

_.sum([1, 2, 3, 4]);
// → 10

_.subtract(10, 3);
// → 7
Try It Yourself

How It Works

  1. Reduce. Folds the array left-to-right with _.add.
  2. Sum. _.sum is clearer for “total this array.”
  3. Subtract. Sibling helper for difference.
  4. Choose. Two values → add; many values → sum.
Compatibility

Browser & Runtime Support

_.add is a Lodash 4.x Math helper. It runs anywhere Lodash runs — modern browsers (CDN or bundle) and Node.js / Bun / Deno with npm install lodash. Native cousin: the + operator (same float math; different undefined defaults).

✓ Stable · Lodash 4.x

_.add()

Available in [email protected] full builds and the lodash/add 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
_.add Lodash 4.x+

Bottom line: Safe for production once Lodash is loaded. Prefer import add from "lodash/add" for smaller builds. Great as a pairwise adder or reduce callback.

Frequently Asked Questions

It adds augend and addend. Official example: _.add(6, 4) → 10.
If only one is undefined, Lodash returns the other unchanged. If both are undefined, it returns 0 (the additive identity).
When either operand is a string, Lodash concatenates (like native +). Force numbers with _.toNumber first.
No. _.add(0.1, 0.2) is 0.30000000000000004 — same IEEE-754 result as native +.
No. BigInt throws Cannot convert a BigInt value to a number. Use native + for BigInt.
Use _.sum(array) to total many values. Use _.add for two values or as a reducer callback.

Next: _.ceil()

Round a number up toward +Infinity with optional precision.

_.ceil() 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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