The Math.trunc()
function returns the integer part of a number by removing any fractional digits.
Syntax
Math.trunc(x)
Parameters
x
- A number.
Return value
The integer part of the given number.
Description
Unlike the other three Math
methods: Math.floor()
, Math.ceil()
and Math.round()
, the way Math.trunc()
works is very simple. It truncates (cuts off) the dot and the digits to the right of it, no matter whether the argument is a positive or negative number.
The argument passed to this method will be converted to number type implicitly.
Because trunc()
is a static method of Math
, you always use it as Math.trunc()
, rather than as a method of a Math
object you created (Math
is not a constructor).
Examples
Using Math.trunc()
Math.trunc(13.37); // 13 Math.trunc(42.84); // 42 Math.trunc(0.123); // 0 Math.trunc(-0.123); // -0 Math.trunc('-1.123'); // -1 Math.trunc(NaN); // NaN Math.trunc('foo'); // NaN Math.trunc(); // NaN
Polyfill
if (!Math.trunc) { Math.trunc = function(v) { v = +v; if (!isFinite(v)) return v; return (v - v % 1) || (v < 0 ? -0 : v === 0 ? v : 0); // returns: // 0 -> 0 // -0 -> -0 // 0.2 -> 0 // -0.2 -> -0 // 0.7 -> 0 // -0.7 -> -0 // Infinity -> Infinity // -Infinity -> -Infinity // NaN -> NaN // null -> 0 }; }
or:
if (!Math.trunc) { Math.trunc = function(v) { v = +v; return (v - v % 1) || (!isFinite(v) || v === 0 ? v : v < 0 ? -0 : 0); }; }
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Math.trunc' in that specification. |
Standard | Initial definition. |
ECMAScript Latest Draft (ECMA-262) The definition of 'Math.trunc' in that specification. |
Living Standard |
Browser compatibility
The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Feature | Chrome | Edge | Firefox | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|---|
Basic support | 38 | Yes | 25 | No | 25 | 8 |
Feature | Android webview | Chrome for Android | Edge mobile | Firefox for Android | IE mobile | Opera Android | iOS Safari |
---|---|---|---|---|---|---|---|
Basic support | Yes | Yes | Yes | 25 | No | Yes | 8 |