difference between two arrays using reduce and the result with the same order (stable)

stable arrays difference

function diff(arr1, arr2) {
  if(arr1.length === 0){
    return arr2;
  }
  if(arr2.length === 0){
    return arr1;
  }
  var newArr = [];
  var deletedArr = [];
  newArr = arr1.concat(arr2);
  return newArr.reduceRight(function(c,l,index){
    var index_l = newArr.indexOf(l);
    if( index_l !== index || deletedArr.indexOf(l) > -1){
      deletedArr.push(l);
    }else{
      c.push(l);
    }    
    return c;
  },[]).sort(function(a,b){
    return newArr.indexOf(a) - newArr.indexOf(b);
  });
}