See: http://careercup.com/question?id=5201559730257920

sort-negs-first.js

//
// See: http://careercup.com/question?id=5201559730257920
//
// Given an array which has positive and negative ints, sort
// the list so that all positives come after negatives, and the
// relative order is preserved.
//
// Input: [-1, 2, 2, -2, -3, 1, 10, 9, -9]
// Output: [-1, -2, -3, -9, 2, 2, 1, 10, 9]
//

/**
 * @param {array} list - The array to modify
 * @return {array} - The modified array
 */
const sortNegsFirst = list => {
  for (let i = 0; i < list.length; i++) {
    if (list[i] > 0) {
      let j = i + 1;
      do {
        if (list[j] < 0) {
          moveNeg(list, j);
          break;
        }
        j++;
      } while (list[j] !== undefined);
    }
  }
  return list;
};

/**
 * Move negative item before all positive items
 * 
 * @param {array} list - The array to modify
 * @param {number} i - The index of the negative item
 */
const moveNeg = (list, i) => {
  let ri = i;
  let li = i - 1;
  while (list[li] !== undefined && list[li] > 0) {
    let temp = list[li];
    list[li] = list[ri];
    list[ri] = temp;
    li--;
    ri--;
  }
};