How to append a smaller list of object in another main list in javaScript

Question

How to append a smaller list of object in another main list after checking only those elements from the smaller list are getting appended which were not previously in main list. I have to do it in javascript.

Answer 1

Would something like the below work?

_.each($testArray, function ($item1){

    var flag = false;
    _.each($setArray, function ($item2){
          if($item1 == $item2)
            flag = true;
    });

    if(flag == false)
        $setArray.push(item1);

});