Way To Add Leading Zeroes To Binary String In JavaScript

I've used .toString(2) to convert an integer to a binary, but it returns a binary only as long as it needs to be (i.e. first bit is a 1). So where: num = 2; num.toString(2) // yiel

Solution 1:

It's as simple as

var n = num.toString(2);
n = "00000000".substr(n.length) + n;

Solution 2:

You could just use a while loop to add zeroes on the front of the result until it is the correct length.

var num = 2,
    binaryStr = num.toString(2);

while(binaryStr.length < 8) {
    binaryStr = "0" + binaryStr;
}

Solution 3:

Try something like this ...

function pad(n, width, z) {
  z = z || '0';
  n = n + '';
  return n.length >= width ? n : new Array(width - n.length + 1).join(z) + n;
}

... then use it as ...

pad(num.toString(2), 8);