This function removes duplicate from the array given as an argument and return an array which contains removed elements.

removeDuplicate2.js

var removeDuplicate2 = function(a) {
  var b = [], i = 1, j, k
  while (i < a.length) {
    k = a.length
    for (j = 0; j < i; j++) {
      if (a[i] === a[j]) {
        b.push(a[j])
        a.splice(i,1)
        break
      }
    }
    if (k == a.length) i++
  }
  return b
}