在此页

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

Number.MAX_SAFE_INTEGER constant represents the maximum safe integer in JavaScript ( 2 53 - 1 ).

For larger integers, consider using BigInt .

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.

特性属性在 Number.MAX_SAFE_INTEGER
可写	no
可枚举	no
可配置	no

描述

MAX_SAFE_INTEGER constant has a value of 9007199254740991 (9,007,199,254,740,991 or ~9 quadrillion). The reasoning behind that number is that JavaScript uses double-precision floating-point format numbers 作为指定在 IEEE 754 and can only safely represent numbers between -(2 53 - 1) and 2 53 - 1 .

Safe in this context refers to the ability to represent integers exactly and to correctly compare them. For example, Number.MAX_SAFE_INTEGER + 1 === Number.MAX_SAFE_INTEGER + 2 will evaluate to true, which is mathematically incorrect. See Number.isSafeInteger() 了解更多信息。

This field does not exist in old browsers. Using it without checking its existence, such as Math.max(Number.MAX_SAFE_INTEGER, 2) , will yield undesired results such as NaN.

因为 MAX_SAFE_INTEGER is a static property of Number , you always use it as Number.MAX_SAFE_INTEGER , rather than as a property of a Number object you created.

Polyfill

if (!Number.MAX_SAFE_INTEGER) {
    Number.MAX_SAFE_INTEGER = 9007199254740991; // Math.pow(2, 53) - 1;
}
				

范例

Return value of MAX_SAFE_INTEGER

Number.MAX_SAFE_INTEGER; // 9007199254740991
				

Numbers higher than safe integer

This returns 2 because in floating points, the value is actually the decimal trailing "1" except for in subnormal precision cases such as zero.

Number.MAX_SAFE_INTEGER * Number.EPSILON; // 2
				

规范

规范
ECMAScript (ECMA-262) The definition of 'Number.MAX_SAFE_INTEGER' 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
MAX_SAFE_INTEGER	Chrome 34	Edge 12	Firefox 31	IE No	Opera 21	Safari 9	WebView Android ≤37	Chrome Android 34	Firefox Android 31	Opera Android 21	Safari iOS 9	Samsung Internet Android 2.0	nodejs 0.12

图例

完整支持

完整支持

不支持

不支持

另请参阅

• Number.MIN_SAFE_INTEGER
• Number.isSafeInteger()
• BigInt

元数据

• 最后修改： 2020 年 8 月 13 日

相关话题

1. 标准内置对象
2. Number
3. 特性
   1. Number.EPSILON
   2. Number.MAX_SAFE_INTEGER
   3. Number.MAX_VALUE
   4. Number.MIN_SAFE_INTEGER
   5. Number.MIN_VALUE
   6. Number.NEGATIVE_INFINITY
   7. Number.NaN
   8. Number.POSITIVE_INFINITY
4. 方法
   1. Number.isFinite()
   2. Number.isInteger()
   3. Number.isNaN()
   4. Number.isSafeInteger()
   5. Number.parseFloat()
   6. Number.parseInt()
   7. Number.prototype.toExponential()
   8. Number.prototype.toFixed()
   9. Number.prototype.toLocaleString()
   10. Number.prototype.toPrecision()
   11. Number.prototype.toSource()
   12. Number.prototype.toString()
   13. Number.prototype.valueOf()
5. 继承：
6. Function
7. 特性
   1. Function.arguments
   2. Function.caller
   3. Function.displayName
   4. Function.length
   5. Function.name
8. 方法
   1. Function.prototype.apply()
   2. Function.prototype.bind()
   3. Function.prototype.call()
   4. Function.prototype.toSource()
   5. Function.prototype.toString()
9. Object
10. 特性
    1. Object.prototype.__proto__
    2. Object.prototype.constructor
11. 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()