在此页

• 句法
• 描述
• Polyfill
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

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.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

句法

Math.sign(x)
					

参数

x

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

返回值

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 被返回。

描述

因为 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.

范例

使用 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
					

规范

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

浏览器兼容性

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. 更新 GitHub 上的兼容性数据

	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 38	Edge 12	Firefox 25	IE No	Opera 25	Safari 9	WebView Android 38	Chrome Android 38	Firefox Android 25	Opera Android 25	Safari iOS 9	Samsung Internet Android 3.0	nodejs 0.12

图例

完整支持

完整支持

不支持

不支持

另请参阅

• Math.abs()
• Math.ceil()
• Math.floor()
• Math.round()
• Math.trunc()

元数据

• 最后修改： May 20, 2020

相关话题

1. 标准内置对象
2. Math
3. 特性
   1. Math.E
   2. Math.LN10
   3. Math.LN2
   4. Math.LOG10E
   5. Math.LOG2E
   6. Math.PI
   7. Math.SQRT1_2
   8. Math.SQRT2
4. 方法
   1. Math.abs()
   2. Math.acos()
   3. Math.acosh()
   4. Math.asin()
   5. Math.asinh()
   6. Math.atan()
   7. Math.atan2()
   8. Math.atanh()
   9. Math.cbrt()
   10. Math.ceil()
   11. Math.clz32()
   12. Math.cos()
   13. Math.cosh()
   14. Math.exp()
   15. Math.expm1()
   16. Math.floor()
   17. Math.fround()
   18. Math.hypot()
   19. Math.imul()
   20. Math.log()
   21. Math.log10()
   22. Math.log1p()
   23. Math.log2()
   24. Math.max()
   25. Math.min()
   26. Math.pow()
   27. Math.random()
   28. Math.round()
   29. Math.sign()
   30. Math.sin()
   31. Math.sinh()
   32. Math.sqrt()
   33. Math.tan()
   34. Math.tanh()
   35. Math.trunc()
5. 继承：
6. Object
7. 特性
   1. Object.prototype.__proto__
   2. Object.prototype.constructor
8. 方法
   1. Object.prototype.__defineGetter__()
   2. Object.prototype.__defineSetter__()
   3. Object.prototype.__lookupGetter__()
   4. Object.prototype.__lookupSetter__()
   5. Object.prototype.hasOwnProperty()
   6. Object.prototype.isPrototypeOf()
   7. Object.prototype.propertyIsEnumerable()
   8. Object.prototype.toLocaleString()
   9. Object.prototype.toSource()
   10. Object.prototype.toString()
   11. Object.prototype.valueOf()
   12. Object.setPrototypeOf()