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The Math.sign() function returns the sign of a number, indicating whether the number is positive, negative or zero.




A number.

Return value

A number representing the sign of the given argument. If the argument is a positive number, negative number, positive zero or negative zero, the function will return 1, -1, 0 or -0 respectively. Otherwise, NaN is returned.


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).

This function has 5 kinds of return values, 1, -1, 0, -0, NaN, which represent "positive number", "negative number", "positive zero", "negative zero" and NaN respectively.

The argument passed to this function will be converted to x type implicitly.


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


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.
    x = +x; // convert to a number
    if (x === 0 || isNaN(x)) {
      return Number(x);
    return x > 0 ? 1 : -1;


Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Math.sign' in that specification.
Standard Initial definition.
ECMAScript 2017 Draft (ECMA-262)
The definition of 'Math.sign' in that specification.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support 38 25 (25) No support 25 9
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support No support No support 25.0 (25) No support No support No support

See also

Document Tags and Contributors

 Last updated by: rwaldron,