convert decimal number to fraction in javascript or closest fraction

Question

So i want to be able to convert any decimal number into fraction. In both forms such as one without remainder like this: 3/5 or with remainder: 3 1/4.

what i was doing is this..

lets say i have number .3435.

• Calculate amount of digits after decimals.
• multiply by 10 with power of the amount before number.
• then somehow find greatest common factor.

Now i don't know how to find GCF. And nor i know how to implement logic to find fraction that represents a number closely or in remainder form if exact fraction doesn't exists.

code i have so far: (testing)

x = 34/35;
a = x - x.toFixed();
tens = (10).pow(a.toString().length - 2);

numerator = tens * x;
denominator = tens;

Answer 1

Your first 2 steps are reasonable.

But what you should do is for the numerator and denominator calculate the Greatest Common Divisor (GCD) and then divide the numerator and denominator with that divisor to get the fraction you want.

GCD is rather easy to calculate. Here is Euclid's algorithm:

var gcd = function(a, b) {
  if (!b) return a;

  return gcd(b, a % b);
};

Edit

I've added a fully working JSFiddle.

Answer 2

Unless you are willing to work on developing something yourself then I would suggest using a library that someone has already put effort into, like fraction.js

Javascript

var frac = new Fraction(0.3435);

console.log(frac.toString());

Output

687/2000

On jsFiddle