Checks if value is a valid array-like length. Loosely based on ECMAScript ToLength. Part of Lodash Lang since 4.0.0 (stable — not deprecated).
Pass the value you want to inspect or convert. Read the return type carefully before you use the result.
Call _.isLength. Start with this line.
_.isLength(value)| Call | What it does |
|---|---|
_.isLength(value) | Primary signature. |
Prefer import isLength from "lodash/isLength" when you want a smaller bundle.
_.isLength(value)| Parameter | Description |
|---|---|
| value | Required. The value to check |
| Return Value | Description |
|---|---|
| * | true if valid length, else false |
3A small non-negative integer is a valid length.
_.isLength(3);
// → true3.typeof 3 === "number".MAX_SAFE_INTEGER.true — valid array-like length.Number.MIN_VALUETiny positive floats are not whole lengths.
_.isLength(Number.MIN_VALUE);
// → falseNumber.MIN_VALUE is the smallest positive float (~5e-324).value % 1 !== 0 — not whole.false.MIN_VALUE with a minimum length of zero.InfinityNon-finite numbers cannot be array lengths.
_.isLength(Infinity);
// → falseInfinity.MAX_SAFE_INTEGER and is not a usable index count.false.-Infinity and NaN also fail."3"Numeric strings look like lengths but fail the type gate.
_.isLength('3');
// → false
_.isLength(Number('3'));
// → true // after parsingtypeof '3' === "string" → immediate fail.Number('3') yields the number 3.true.MAX_SAFE_INTEGEREmpty lengths and the inclusive safe ceiling both pass; one past fails.
_.isLength(0); // → true
_.isLength(Number.MAX_SAFE_INTEGER); // → true
_.isLength(Number.MAX_SAFE_INTEGER + 1); // → false
_.isLength(-1); // → false0 → allowed.MAX_SAFE_INTEGER is the inclusive upper bound.-1 is an integer but never a length._.isLength is a Lodash Lang helper (available since 4.0.0, stable in 4.x). It runs anywhere Lodash runs — modern browsers (via CDN or bundle) and Node.js / Bun / Deno with npm install lodash.
Available in [email protected] full builds and the lodash/isLength modular import. Works in evergreen browsers and current Node LTS when Lodash is installed.
Bottom line: Safe for production once Lodash is on the page or in your bundle. Prefer import isLength from "lodash/isLength" for smaller builds. Native alternative for a similar idea: Number.isSafeInteger(n) && n >= 0.
Check whether a value is classified as a Map object.
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