如何获取Javascript中浮点数的小数位? [英] How do I get the decimal places of a floating point number in Javascript?

问题描述

我想要拥有的是与Number.prototype.toPrecision()几乎相反的东西，这意味着当我拥有数字时，它拥有多少个小数?例如

What I would like to have is the almost opposite of Number.prototype.toPrecision(), meaning that when i have number, how many decimals does it have? E.g.

(12.3456).getDecimals() // 4

推荐答案

对于想知道如何更快地执行此操作(不转换为字符串)的人，以下是一种解决方案:

For anyone wondering how to do this faster (without converting to string), here's a solution:

function precision(a) {
  var e = 1;
  while (Math.round(a * e) / e !== a) e *= 10;
  return Math.log(e) / Math.LN10;
}

涵盖边缘情况的更完整解决方案:

a more complete solution with edge cases covered:

function precision(a) {
  if (!isFinite(a)) return 0;
  var e = 1, p = 0;
  while (Math.round(a * e) / e !== a) { e *= 10; p++; }
  return p;
}

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