check the same elements from 2 arrays.

compare.js

// check the same elements from 2 arrays.

function compare(a, b){
  var set = [];
  var i = 0, j = 0;
  var jHit = -1;
  while (i < a.length && j < b.length) {
    if (a[i]==b[j]){
      set.push(a[i]);
      i = i+1;
      jHit = j;
    }
    j = j+1;
    if (j == b.length) {
      i=i+1;
      j=jHit+1;
    }
  }
  return set;
}