The Math.trunc()
function returns the integer part of a number by removing any fractional digits.
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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).
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) { return v < 0 ? Math.ceil(v) : Math.floor(v); }; }
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
Specifications
Specification |
---|
ECMAScript (ECMA-262) The definition of 'Math.trunc' in that specification. |
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.
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
trunc | Chrome Full support 38 | Edge Full support 12 | Firefox Full support 25 | IE No support No | Opera Full support 25 | Safari Full support 8 | WebView Android Full support 38 | Chrome Android Full support 38 | Firefox Android Full support 25 | Opera Android Full support 25 | Safari iOS Full support 8 | Samsung Internet Android Full support 3.0 | nodejs Full support 0.12 |
Legend
- Full support
- Full support
- No support
- No support