在javascript中减去长数字 [英] Subtracting long numbers in javascript

问题描述

为什么以下脚本中的q == 0？

Why is q == 0 in the following script?

<script>
  var start = 1234567890123456789;
  var end =   1234567890123456799;
  var q = end - start;
  alert(q);
</script>

我认为结果应该是10.减去这两个数字的正确方法是什么？

I would think the result should be 10. What is the correct way to subtract these two numbers?

推荐答案

因为JavaScript中的数字是浮点数。它们的精度有限。

Because numbers in JavaScript are floating-point. They have limited precision.

当JavaScript看到一个很长的数字时，它会将它四舍五入到它可以表示为64位浮点数的最近数字。在您的脚本中，开始和结束将四舍五入为相同的值。

When JavaScript sees a very long number, it rounds it to the nearest number it can represent as a 64-bit float. In your script, start and end get rounded to the same value.

alert(1234567890123456789);   // says: 1234567890123456800
alert(1234567890123456799);   // says: 1234567890123456800

没有内置的方法可以对大整数进行精确算术，但是你可以使用BigInteger库，例如这一个。

There's no built-in way to do precise arithmetic on large integers, but you can use a BigInteger library such as this one.

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