How to get event onkeyup in input id two using javascript?

Question

How to get event onkeyup in input id="two" using javascript?

I not permission to edit in function test_1_fn() and input id="one"

So, how can i edit in input id="two" or function test_2_fn() to get value from input id="two" for alert as a onkeyup ?

Remark : User can fill text into input id="one" only.

<input id="one" onkeyup="test_1_fn()"><br>
<script>
    function test_1_fn() {
        var one_val = document.getElementById("one").value;
        document.getElementById("two").value = one_val;
    }
</script>
<input id="two" onkeyup="test_2_fn()"><br>
<script>
    function test_2_fn() {
        var two_val = document.getElementById("two").value;
        alert(two_val);
    }
</script>

@ Jonas W. -- first when i fill text into input `id="one"` then input `id="two"` will change value. it's ok ? — mamong mamiw, Dec 02 '17 at 15:53
When input `id="two"` change i want to alert value in input `id="two"` too. — mamong mamiw, Dec 02 '17 at 15:53
*I want to alert value in input `id="two"`* : I don't understand what that means. `alert()` opens a popup message, it cannot be *"in"* an `input`. — trincot, Dec 02 '17 at 16:02

score 0 · Answer 1 · answered Dec 02 '17 at 16:00

The best method would be probably a MutationObserver as changing an elements property via javascript does not trigger any events on the element. However as thats quite complicated the noobish method would be:

var before, el = document.getElementById("two");
setInterval(function(){
  if(before && el.value != before){
    alert(el.value);
  }
  before = el.value;
}, 50);

However i still don't get why youre not simply doing:

document.getElementById("one").addEventListener("keyup", function(){
 alert(this.value);
});

How to get event onkeyup in input id two using javascript?

1 Answers1