Web/JavaScript/Reference/Global objects/Math/sign

The Math.sign() function returns either a positive or negative +/- 1, indicating the sign of a number passed into the argument. If the number passed into Math.sign() is 0, it will return a +/- 0. Note that if the number is positive, an explicit (+) will not be returned.

Syntax

Math.sign(x)

Parameters

x: A number. If this argument is not a number, it is implicitly converted to one.

Return value

A number representing the sign of the given argument:

If the argument is positive, returns 1.
If the argument is negative, returns -1.
If the argument is positive zero, returns 0.
If the argument is negative zero, returns -0.
Otherwise, NaN is returned.

Description

Because sign() is a static method of Math, you always use it as Math.sign(), rather than as a method of a Math object you created (Math is not a constructor).

Polyfill

if (!Math.sign) {
  Math.sign = function(x) {
    // If x is NaN, the result is NaN.
    // If x is -0, the result is -0.
    // If x is +0, the result is +0.
    // If x is negative and not -0, the result is -1.
    // If x is positive and not +0, the result is +1.
    return ((x > 0) - (x < 0)) || +x;
    // A more aesthetic pseudo-representation:
    //
    // ( (x > 0) ? 1 : 0 )  // if x is positive, then positive one
    //          +           // else (because you can't be both - and +)
    // ( (x < 0) ? -1 : 0 ) // if x is negative, then negative one
    //         ||           // if x is 0, -0, or NaN, or not a number,
    //         +x           // then the result will be x, (or) if x is
    //                      // not a number, then x converts to number
  };
}

In the above polyfill, no extra type-coercing is needed to make (x > 0) or (x < 0) numbers because subtracting them from each other forces a type conversion from booleans to numbers.

Examples

Using Math.sign()

Math.sign(3);     //  1
Math.sign(-3);    // -1
Math.sign('-3');  // -1
Math.sign(0);     //  0
Math.sign(-0);    // -0
Math.sign(NaN);   // NaN
Math.sign('foo'); // NaN
Math.sign();      // NaN

Specifications

Specification
ECMAScript (ECMA-262)The definition of 'Math.sign' in that specification.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
`sign`	Chrome Full support 38	Edge Full support 12	Firefox Full support 25	IE No support No	Opera Full support 25	Safari Full support 9	WebView Android Full support 38	Chrome Android Full support 38	Firefox Android Full support 25	Opera Android Full support 25	Safari iOS Full support 9	Samsung Internet Android Full support 3.0	nodejs Full support 0.12

Legend

Full support: Full support
No support: No support