Javascript (ES6) convert number into string array of powers of 2

Question

Is there any smart inliner/one-liner (ES6) in transforming a number (integer) into a string array which got the number's bit position of its binary powers (pow(2,x))? i.e.

13  =>    ["1","3","4"]    //   (pow(2,1) + pow(2,3)  + pow(2,4))  = 13

Answer 1

If you actually want an array of the powers of 2 which will result in the number, then for 13, you'd want:

2 ** 0 = 1
2 ** 2 = 4
2 ** 3 = 8
1 + 4 + 8 = 13

That is - [0, 2, 3] are the powers which result in 13.

.toString(2) turns a number into its binary equivalent, so you can take the elements of that string which are 1s:

const num = 13;
const arr = [];
[...num.toString(2)].reverse().forEach((bit, i) => {
  if (bit === '1') {
    arr.push(i);
  }
});
console.log(arr);

Like all JS code, it's possible to squash into one line, but it'd be pretty silly - better to write clean and readable code without regard to line length:

const num = 13; const arr = []; [...num.toString(2)].reverse().forEach((bit, i) => {   if (bit === '1') {   arr.push(i); } }); console.log(arr);