Find highest number of decimal places in String

Question

The example string(s) can look like that:

• 1. "3.0000+3"
• 2. "3.00+3.00"
• 3. "3.00+3.000"

I want to find the highest amount of decimal places out of the numbers inside 1 string

Answer 1

The most straight-forward way to do this is iterating over the string, checking for the occurence of a dot and from there on count the number of digits up to the next character that's NOT a number or the end of the string. Since your string contains multiple numbers you need to add a variable which holds the highest amount of decimal places. e.g.

var str = "3.00+3.000";

function getDecimalPlaces(numb) {
  var highest = 0;
  var counter = 0;
  for (a = 0; a < numb.length; a++) {
    if (numb.charAt(a - 1) == ".") {
      do {
        counter++;
        a++;
      }
      while (!isNaN(numb.charAt(a)) && a < numb.length);
    }
    if (counter > highest) {
      highest = counter;
    }
    counter = 0;
  }
  return highest;
}

console.log(str + " has " + getDecimalPlaces(str) + " decimal places");

This can be made a bit more elegant by using a regular expression in conjunction with the .match() method. This searches a string for a given pattern and returns an array of results.

var str = "3.00+3.000";

console.log(str.match(/(\.)([0-9]+)/g));

This will return an array like:

[".00", ".000"]

By comparing the length of it's elements - minus 1 since it includes the dot - we can get the number of decimal places using this nifty short function:

var str = "3.00+3.000";
var highest = str.match(/(\.)([0-9]+)/g).reduce(function(a, b) {
    return Math.max(a.length - 1, b.length - 1);
});
console.log(str + " has " + highest + " decimal places");