Javascript: how to get micronumbers in decimal format

Question

I have simple function that calculates number of decimals, eg. _d(0.01) = 2, _d(0.001) = 3 and so on.

We added some new coins to our system that have 0.00000001 quantity and function broke.

Here is why: 0.00000001.toString() = 1e-8, so I cant split it it by '.' and calculate length of second part as I did before.

So the question is - how to get string '0.00000001' out of 0.00000001 number easiest way.

EDIT I didnt mean exactly '0.00000001', I meant any micronumber to decimal without exp. Some function _d(x) that would work _d(0.000000000012) = '0.000000000012'and so on. What usually toString() does to large (but not too large) numbers.

Answer 1

Use toFixed() with a large number of digits, then count the number of zeroes after the decimal point.

function _d(num) {
    var str = num.toFixed(100);
    var fraction = str.split('.')[1];
    var zeros = fraction.match(/^0*/)[0].length;
    return zeros + 1;
}
console.log(_d(0.1));
console.log(_d(0.01));
console.log(_d(0.000000001));

Answer 2

Do you want some thing like this

function decimalPlaces(num) {
  var match = (''+num).match(/(?:\.(\d+))?(?:[eE]([+-]?\d+))?$/);
  if (!match) { return 0; }
  return Math.max(
       0,
       // Number of digits right of decimal point.
       (match[1] ? match[1].length : 0)
       // Adjust for scientific notation.
       - (match[2] ? +match[2] : 0));
}

console.log(decimalPlaces(0.000000001))

Answer 3

First off, I got some inspiration for this answer from here: How to avoid scientific notation for large numbers in JavaScript?

You can convert the number to a strong and then check for str.indexOf("e"). If true, then just return the scientific notation part of the string. For example:

  function _d() {
    // your current function here
    if (str.indexOf("e")) {
      var something = str.split("-")[1];
      return something;
    }
  }

EDIT: I was working on this before your last comment to me, so this returns a string of the number, which I thought was what you wanted. Leaving aside the point about significant digits, which is meaningful and correct but does not solve your problem, try this. We take the number, convert to string, if that string is not scientific notation then the answer is trivial. If it is scientific notation, then split the string twice (once on "e-" and then split the zeroth array on "." Add str[1]-1 zeroes to the lead of the number and add the digits to the end.

function _d(arg) {
  var str = arg.toString();
  if (str.indexOf("e-")) {
    var digits = str.split("e-")[0];
    var zeroes = str.split("e-")[1];
    var zero = Number(zeroes);
    var each = digits.split(".");
    var something = "0.";
    for (var i = 0; i < zeroes-1; i++) {
      something += "0";
    }
    for (var j = 0; j < each.length; j++) {
      something = something + each[j];
    }
    return something;
  }
}

This won't work with very large numbers or very small negative numbers. And its pretty convoluted.

Answer 4

To keep it as the full decimal:

Number(0.000001)
// 0.000001

To show it as a string:

0.000001.toFixed(6)
// "0.000001"

Answer 5

The other way is to use .toString() and then look for .length-2(2 characters - '0.'. It should give you the number of zeros.

The advantage of this method is you don't need to know the number of maximum decimals in the number.