我們的志工尚未將此文章翻譯為 正體中文 (繁體) 版本。加入我們，幫忙翻譯！
The Number.MAX_SAFE_INTEGER constant represents the maximum safe integer in JavaScript (253 - 1).
Property attributes of Number.MAX_SAFE_INTEGER |
|
|---|---|
| Writable | no |
| Enumerable | no |
| Configurable | no |
Description
The MAX_SAFE_INTEGER constant has a value of 9007199254740991. The reasoning behind that number is that JavaScript uses double-precision floating-point format numbers as specified in IEEE 754 and can only safely represent numbers between -(253 - 1) and 253 - 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() for more information.
Because 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.
Examples
Number.MAX_SAFE_INTEGER // 9007199254740991 Math.pow(2, 53) - 1 // 9007199254740991
Specifications
| Specification | Status | Comment |
|---|---|---|
| ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Number.MAX_SAFE_INTEGER' in that specification. |
Standard | Initial definition. |
| ECMAScript 2017 Draft (ECMA-262) The definition of 'Number.MAX_SAFE_INTEGER' in that specification. |
Draft |
Browser compatibility
| Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
|---|---|---|---|---|---|
| Basic support | 34 | 31 (31) | No support | (Yes) | 9 |
| Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
|---|---|---|---|---|---|---|
| Basic support | (Yes) | (Yes) | 32.0 (32) | No support | No support | 9 |