javascript 大整数舍入，因为精度?(为什么?) [英] javascript large integer round because precision? (why?)

问题描述

如果你这样做

for(var i = 0; i < 30; i++){console.log(i + " == " + 78764357878563800 + " ? ");console.log((78764357878563790+i) == 78764357878563800);}

您开始比较从 78764357878563790 到 78764357878563790+29 的值，所以...就像您运行它时看到的那样，您会从 i = 8 到 24 得到真值.

You start comparing values from 78764357878563790 to 78764357878563790+29, so... like you see if you run it, you get true from i = 8 to 24.

所以我不知道我是否不明白，但不应该存在 maxint(我不知道)和 maxint-1 ???然后 max 与 maxint-1 不同?

So I don't know if I don't get it, but isn't supposed to exist the maxint (which I dont know) and a maxint-1??? and then max be different than maxint-1?

我想这就像浮点数一样精度......但这不应该只命中浮点数，例如，数字+1总是给出后继?(所以在上面的例子中，如果 i = 78764357878563790 并加上 i++，那么你就进入了无限循环.

I suppose this is precision like floating numbers... but that isn't supposed to only hit floating numbers and for example, number+1 always gives the successor? (so in the example above, if i = 78764357878563790 and add i++, then you enter an infinite loop.

我事先知道浮点数存在这种类型的数字间距，但从来没有遇到整数不能代表 i+1 和 i-1 的情况(我一直认为 unsigned maxint + 1 会携带并给出0).

I know before hand that this type of spacing between numbers exist for floating points, but never hit a case where also the integers cant represent i+1 and i-1 (I always thinked that unsigned maxint + 1 would carry and give 0).

任何建议:

• js 中的最大数和前数是多少.
• 如何处理或了解整数的这种行为何时开始发生.
• 如何处理如此大的数字以及比这更大的数字会很好.

推荐答案

Javascript 中没有整数.

There are no integers in Javascript.

数字是双精度浮点数，精度为 15-16 位.这与您的结果一致.

Numbers are double precision floating point, which gives you a precision of 15-16 digits. This is consistent with your results.

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