JavaScript大整数轮因为精度？ （为什么？） [英] javascript large integer round because precision? (why?)

问题描述

如果您在chrome或safari中输入78764357878563812，那么您可以获得

如果您这样做

<$ p $ （i = 0; i <30; i ++）{console.log（i +==+ 78764357878563800 +？）; console.log（（78764357878563790 + i） == 78764357878563800）;}

您将78764357878563790与78764357878563790 + 29进行比较，所以...就像你看到你是否运行它一样，你从i = 8变为24。

所以我不知道我是否得到它，但不应该存在maxint（我不知道）和maxint-1？然后最大不同于maxint-1？

我认为这是像浮动数字一样的精确度......但是这不应该只是浮动数字，例如数字+ 1总是给继任者？ （所以在上面的例子中，如果我= 78764357878563790并添加了i ++，那么你输入了一个无限循环。

我之前知道这种类型的数字间隔存在浮点数，但从来没有遇到过整数不能代表i + 1和i-1的情况（我一直认为无符号maxint + 1会携带并给出0）。

<
$ b

• 这是最大数字，js中的前数字是什么。


• 如何处理或知道整数行为何时开始发生。


• 如何处理这个大数字，并且比这更大。

解决方案

Javascript中没有整数。

双精度浮点数，它提供15-16位数的精度，这与您的结果一致。

if you type 78764357878563812 in chrome or in safari, then you get

If you do

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

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.

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

I suppose this is precision like floating numbers... but that isnt supposed to only hit floating numbers and for example number+1 always give the succesor? (so in the example above, if i = 78764357878563790 and add i++, then you enter an infinite loop.

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).

Any suguestions in:

• which is the max number and what is the anterior number in js.
• how to handle or know when this behaviour for integers will start happening.
• how to handle this large numbers and more big than this would be nice.

解决方案

There are no integers in Javascript.

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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