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87

How do I get the decimal places of a floating point number in Javascript?

rated 0 times [ 89] [ 2] / answers: 1 / hits: 48041 / 13 Years ago, sun, march 4, 2012, 12:00:00

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

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brodyfrancisi

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answered 13 Years ago brynneg · Accepted Answer

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;

}

Edit: 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;

}