Advanced diff between arrays

diff.js

var diff = function(a, b) {
  var c = [], dels = [], delsIndex = [];
  var i = 0, j = 0, k,
  x, y, z;
  var t = 0; //debug

  while (i < a.length || j < b.length) {
    x = a[i];
    y = b[j];
    t++;

    if (x === y) { // =
      c.push({
        diff: "=",
        val: x
      });
      i++;
      j++;
    } else { // +, - or ~
      k = dels.indexOf(y);
      if (k >= 0) { // ~
        z = dels.splice(k, 1)[0];
        delsIndex.shift();
        c.push({
          diff: "~",
          val: z
        });
        j++;
      } else {
        if (x === undefined || a.indexOf(y) < 0) {
          c.push({
            diff: "+",
            val: y
          });
          j++;
        } else {
          dels.push(x);
          delsIndex.push(c.length + dels.length - 1);
          i++;
        }
      }
    }

    if (t > a.length + b.length) {
      console.log("diff failed");
      break;
    }
  }

  while (dels.length > 0) {
    c.splice(delsIndex.shift(), 0, {
      diff: "-",
      val: dels.shift()
    });
  }

  return c;
};
var c = diff([ 10, 1, 4, 3, 2, 7, 5, 8, 1, 2, 4], [1, 3, 4, 10, 2, 0, 6, 1, 4]), cc = [];
$.each(c, function(i, v) {
  cc.push(v.diff+v.val);
});
console.log(cc);