From other searches, I found that this problem is called 'Hamming Weight' or 'Population Count'. There are lot of answers out there given with so many statistics? I need to find the solution in a simple way? Complexity is not a big deal. Is there any in-built function in JavaScript like Java's Integer.bitCount?

I'm currently doing this as follows.

var binary = 3;
var original = binary;
var count = 0;
while(binary>0)
{
    binary = binary >> 1 << 1;
    if(original-binary==1)
        count++;
    original = binary >> 1;
    binary = original;
}

Is there a better, more simple as well as elegant way for this?

From other searches, I found that this problem is called 'Hamming Weight' or 'Population Count'. There are lot of answers out there given with so many statistics? I need to find the solution in a simple way? Complexity is not a big deal. Is there any in-built function in JavaScript like Java's Integer.bitCount?

I'm currently doing this as follows.

var binary = 3;
var original = binary;
var count = 0;
while(binary>0)
{
    binary = binary >> 1 << 1;
    if(original-binary==1)
        count++;
    original = binary >> 1;
    binary = original;
}

Is there a better, more simple as well as elegant way for this?

• javascript
• binary

• 3 If it's truly a string, str.split('1').length, but that's not javascript at all is it, it's Java – adeneo Commented Jul 1, 2014 at 9:15
• related to code review(codereview.stackexchange.com/questions) – Govind Singh Commented Jul 1, 2014 at 9:18
• @adeneo sorry wrong details. I need to perform this on a number. – Foreever Commented Jul 1, 2014 at 9:19
• Then it's numb.toString().split('1').length, tada ! – adeneo Commented Jul 1, 2014 at 9:21
• Prefer over what, the code you've posted is not javascript, and you're asking for javascript, it's sorta hard to understand what you really want ? – adeneo Commented Jul 1, 2014 at 9:23

5 Answers 5

try this

var binary = 10;
var result = binary.toString(2); //Converts to binary
var count = result.split(1);//  count -1 is your answer
alert((result.split('1').length-1));

can also be written as

(binary.toString(2).split('1').length-1)

toString(2)  : helps to split it in a base2 format which is binary, can do this in a range of 2- 36 (iam not sure about the range) 

If you want to count 1 digit in binary representation we can use regular expression like this.

number.toString(2).match(/1/g).length

A simple way without using built-in functions:

function f(n){
    let i = 0;
    do if(n&1) ++i; while(n>>=1)
    return i;
}

// example:
console.log(f(7)); // 3

  function numOfOnes(n) {
    if(n === 0) return n;
    return (n & 1) + numOfOnes(n >>= 1);
  }

Basically this approach belongs to recursive call.
It has the base condition when no number to evaluate.
Otherwise it calls itself on (n >>= 1) and add last digit (n & 1) to result.
eg. 7 has binary representation 111 = 1+1+1 = 3
17 has binary representation 10001 = 1+0+0+0+1 = 2

function countOnesInDecimal(num) {
  let count = 0;
  let binary = num.toString(2);
  const splitted = binary.split('');
  for (const iterator of splitted) {
    if (iterator === `1`) {
      count += 1;
    }
  }

  return count;
}
console.log(countOnesInDecimal(3));