Example 1 — Official Average
Average four numbers from the docs.
Lodash
_.mean([4, 2, 8, 6]);
// → 5How It Works
- Sum.
4 + 2 + 8 + 6 = 20. - Length. Four elements.
- Divide.
20 / 4 = 5. - Result. Arithmetic mean of the array.
Lodash _.mean() Method
Definition
Computes the arithmetic mean of the values in array (sum ÷ length). Part of Lodash 4.x Math (since 4.0.0).
Pass the numbers or collection shown below. Check the return value before you chain another math helper.
Syntax
Call _.mean. Start with this line.
Lodash
_.mean(array)| Call | What it does |
|---|---|
_.mean(array) | Primary signature. |
Prefer import mean from "lodash/mean" when you want a smaller bundle.
Library declarations
Lodash
_.mean(array)Parameters
| Parameter | Description |
|---|---|
| array | Required. Array of values to average |
Return Value
| Return Value | Description |
|---|---|
| * | Mean number, or NaN if empty/nullish |
Lodash Examples
Example 2 — Empty Array Returns NaN
No values means no defined average.
Lodash
_.mean([]);
// → NaN
_.mean(null);
// → NaN
Number.isFinite(_.mean([]));
// → falseHow It Works
- Empty. Sum is
0, length is0. - Divide.
0 / 0→NaN. - Nullish. Same fallback for
null/undefinedinput. - Guard. Check with
Number.isFinitebefore display.
Example 3 — undefined and null Holes
Missing values affect the divisor.
Lodash
_.mean([10, undefined, 20]);
// → 10 // (10 + 20) / 3
_.mean([10, null, 20]);
// → 10 // (10 + 0 + 20) / 3
_.mean([10, 20]);
// → 15How It Works
- undefined. Skipped in the sum, still counted in length.
- null. Coerces to
0in the sum. - Clean list. Only real numbers → expected mid-point.
- Fix. Filter holes first if you want “known values only.”
Example 4 — String Pitfall
One string can break the average via concatenation.
Lodash
_.mean([10, "20", 30]);
// → 34010 // concat during sum, then ÷ 3
_.mean([10, 20, 30].map(Number));
// → 20
_.mean([10, _.toNumber("20"), 30]);
// → 20How It Works
- Concat.
10 + "20"becomes"1020", then more joining. - Divide. That huge string coerces to a number ÷ length.
- Coerce. Map with
Numberor_.toNumber. - Rule. Keep arrays numeric before averaging.
Example 5 — vs _.sum and _.meanBy
Pick the helper that matches the job.
Lodash
var nums = [4, 2, 8, 6];
var rows = [{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }];
_.mean(nums);
// → 5
_.sum(nums);
// → 20
_.meanBy(rows, "n");
// → 5How It Works
- mean. Average of raw numbers.
- sum. Total without dividing.
- meanBy. Average a field on objects.
- Choose. Numbers → mean; objects → meanBy; total → sum.
Compatibility
Browser & Runtime Support
_.mean is a Lodash 4.x Math helper (since 4.0.0). It runs anywhere Lodash runs — modern browsers (CDN or bundle) and Node.js / Bun / Deno with npm install lodash. Native cousin: sum with reduce then divide by length.
Stable · Lodash 4.0.0+
_.mean()
Available in [email protected] full builds and the lodash/mean 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 supportMozilla Firefox Supported · Desktop & Mobile
Full supportApple Safari Supported · macOS & iOS
Full supportMicrosoft Edge Supported · Chromium
Full supportInternet Explorer No native support · Use a polyfill
PolyfillOpera Supported · Modern versions
Full supportSamsung Internet Supported · Android
Full supportBun Supported · JavaScript runtime
SupportedDeno Supported · JavaScript runtime
SupportedNode.js Supported · Server runtime
SupportedAndroid WebView Supported · Modern WebView
Full support_.mean Lodash 4.0+
Bottom line: Safe for production once Lodash is loaded. Prefer import mean from "lodash/mean" for smaller builds. Use for simple numeric averages; use meanBy for object fields.
Frequently Asked Questions
It computes the arithmetic mean of the values in array. Official: _.mean([4, 2, 8, 6]) → 5.
NaN — not 0 or undefined. Empty or nullish input yields NaN (effectively 0 / 0).
mean averages the elements themselves. meanBy averages a projected value per element (function or property path).
sum returns the total. mean returns total / length.
undefined is skipped in the sum but still counted in length, which pulls the average down. Prefer filtering first when that matters.
Yes. A string switches + to concatenation during the sum, so the average can become nonsense. Coerce with Number / _.toNumber first.
Next: _.meanBy()
Average object fields with an iteratee or property path.
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