什么是JavaScript的最大整数值，一个号码可以去不失precision？ [英] What is JavaScript's highest integer value that a Number can go to without losing precision?

问题描述

这是由语言定义的？是否有一个定义的最大？它是在不同的浏览器有什么不同？

Is this defined by the language? Is there a defined maximum? Is it different in different browsers?

推荐答案

+/- 9007199254740991

ECMA 8.5节 - 数字

请注意，所有的正和负整数，其量值是不大于2 ^{在数式（事实上，整数0具有两个重presentations 53功能}重新presentable， + 0和-0）。

Note that all the positive and negative integers whose magnitude is no greater than 2⁵³ are representable in the Number type (indeed, the integer 0 has two representations, +0 and −0).

他们是64位浮点值，最大的精确积分值是2 ⁵³ -1，或 9007199254740991 。在ES6，这被定义为<一href=\"https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER\">Number.MAX_SAFE_INTEGER.

They are 64-bit floating point values, the largest exact integral value is 2⁵³-1, or 9007199254740991. In ES6, this is defined as Number.MAX_SAFE_INTEGER.

请注意，该位运算符和移位运算32位整数操作，所以在这种情况下，最大安全整数2 ³¹ -1或2147483647

Note that the bitwise operators and shift operators operate on 32-bit ints, so in that case, the max safe integer is 2³¹-1, or 2147483647.

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测试一下！

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Test it out!

var x = 9007199254740992;
var y = -x;
x == x + 1; // true !
y == y - 1; // also true !
// Arithmetic operators work, but bitwise/shifts only operate on int32:
x / 2;      // 4503599627370496
x >> 1;     // 0
x | 1;      // 1

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