SOURCE

var arr = [4, 2, 5, 1, 3];
function fun1() {
  var len = arr.length;
  console.time('Tstart');

  console.timeEnd('Tend');
}
function diff(arr1, arr2) {
  //储存新数组  
  var newArr = [];
  //遍历这两个数组  
  for (var i = 0; i < arr1.length; i++) {
    if (arr2.indexOf(arr1[i]) === -1) {
      newArr.push(arr1[i]);
    }
  }
  for (var j = 0; j < arr2.length; j++) {
    if (arr1.indexOf(arr2[j]) === -1) {
      newArr.push(arr2[j]);
    }
  }
  return newArr;
}

diff([1, 2, 3, 5], [1, 2, 3, 4, 5])