Partition.js

// One pointer
var partition1 = function(array, start, end) {
  if(start === end) {
    return;
  }
  // Choose the first element as pivot
  var pivot = array[start];
  // last position which is smaller than pivot
  var small = start;
  for(var index = start + 1; index <= end; index++) {
    if(array[index] < pivot) {
      small++;
      array[small] = [array[index], array[index]=array[small]][0];
    }
  }
  
  array[small] = [array[start], array[start]=array[small]][0];
}

var partition2 = function(array, start, end) {
  // 2 pointers
  if(start === end) {
    return;
  }
  
  var pivot = array[start];
  var i = start + 1;
  var j = end;
  while(index <= j) {
    while(array[i] < pivot && i < j) {
      i++;
    }
    
    while(array[j] >= pivot && i < j) {
      j--;
    }
    
    array[i] = [array[j], array[j]=array[i]][0];
    i++;
    j--;
  }
  
  array[i] = [array[start], array[i]=array[start]][0];
}

var partition3 = function(array, target, start, end) {
  // 3 ways partition
  if(start === end) {
    return;
  }
  
  var i = start,
      j = end
      index = start;
  
  while(i < j) {
    if(array[index] < target) {
      if(i != index) {
        array[i] = [array[index], array[index]=array[i]][0];
      }
      i++;
    } else if(array[index] > target){
       if(j != index) {
        array[j] = [array[index], array[index]=array[j]][0];
      }
      j--;
    }
    index++;
  }
}