Javascript Number twos(n)

function nzero(n, flag) {
  let zeros = '';
  const ch = flag ? '0' : '1';
  while (n-- > 0) {
    zeros += ch;/*w w w  .ja  v  a  2s  . co m*/
  }
  return zeros;
}
Number.prototype.twos = function twos(n) {
  const zeros = nzero(n, this > 0);
  return `${zeros}${Math.abs(this).toString(2)}`.substr(-n);
};

Number.prototype.twos = function(n) {
  let c = this < 0 ? '1' : '0';
  return ((this < 0 ? '1' : '') + Math.abs(this).toString(2)).pad(c, n).slice(-n);
}

Number.prototype.twos = function(n) { 
  var bin         = Math.abs(this.valueOf()).toString(2),
      isNegative  = (this.valueOf() < 0);

  if(bin.length > n) return bin;
  
  if(isNegative)//from   www. ja  v a  2 s.c o  m
    while(bin.length < n) bin = '1'+bin;
  else
    while(bin.length < n) bin = '0'+bin;

  return bin;
}

// I feel like this might be the solution:
//   ((this & (2 ** n - 1)) & this)
// but it also requires left padding with zeros,
// which feels wrong, so I might as well just do something
// else. Unsure if there's a binary trick I don't know.
Number.prototype.twos = function (n) {
  // return (this < 0 ? '1' : '0') + Math.abs(this).toString(2).slice(n * -1 + 1)
  const compliment = ((this & (2 ** n - 1)) & this)
  return ('0'.repeat(32) + compliment.toString(2)).slice(-n)
}

Number.prototype.twos = function(n) {
  //You may assume for this excercise that  n >= 2... 

  let bits = this.toString(2);
  let pad = '0';
  let neg = bits[0] === '-' ? true : false;
  if (neg) {//from w  w w  .j a  va  2  s.  c o  m
    bits = bits.substring(1);
    pad = '1';
  }
  while (bits.length < n) bits = pad + bits;
  return bits;
}

//http://www.codewars.com/kata/523fba59cb9aaaef4f000135/train/javascript

Number.prototype.twos = function(n) {
  //You may assume for this excercise that  n >= 2... 
  var work = this.toString(2);
  var work2 = ""
  var result;/*from w  w w .j av a 2  s  . c  o  m*/
  for (var i = 0; i < work.length; i++){
    if (work[i] === "-"){
      work2 += "1";
    }
    else {
      work2 += work[i];
    }
  }
  if (work2.length >= n){
    return work2.slice(work2.length-n, work2.length);
  }
  else {
    if (work[0] === "-"){
      while (work2.length < n){
        work2 = "1" + work2;
      }
    }
    else {
      while (work2.length < n){
        work2 = "0" + work2;
      }
    }
    return work2;
  }
}