How to convert a binary fraction number into decimal fraction number?

Question

I want to convert a binary fraction number into decimal in JavaScript, like 0.00011001100110011001100. But I found that there is no radix for parseFloat as for parseInt, So how can I do that?

Answer 1

There may well be a better way, but here's a generic function with pick your own radix goodness

var binFraction = function(s, radix) {
    radix = radix || 2;
    var t = s.split('.');
    var answer = parseInt(t[0], radix);
    var d = t[1].split('');
    for(var i = 0, div = radix; i < d.length; i++, div = div * radix) {
        answer = answer + d[i] / div;
    }
    return answer;
}

No error checking done on the input, or the radix, but it seems to work OK

Answer 2

I want to convert a binary fraction number into decimal in JavaScript, like 0.00011001100110011001100. But I found that there is no radix for parseFloat as for parseInt, So how can I do that?

We can build a parseFloatRadix() function like this:

function parseFloatRadix(num, radix) {
  return parseInt(num.replace('.', ''), radix) /
    Math.pow(radix, (num.split('.')[1] || '').length)
}

This stackowerflow answer provides more detail. Demo code below.

function parseFloatRadix(num, radix) {
  return parseInt(num.replace('.', ''), radix) /
      Math.pow(radix, (num.split('.')[1] || '').length)
}

test('0.00011001100110011001100', 2, 0.09999990463256836);

function test(num, radix, expected){
  let result = parseFloatRadix(num, radix);
  console.log(num + ' (base ' + radix +') --> ' + result + 
    (result === expected ? ' (OK)' : ' (Expected ' + expected + ')'));
}