I am trying to trigger a function when value of input_1 textbox changes.

i.e. getElementById('input_1').onchange results in object is not a function.

HTML

<form method=GET id=game_form></form>

<table border=1 style=background-color:#FFFFCC;border-collapse:collapse;border:1px solid #FFCC00;color:#000000;width:100 cellpadding=3 cellspacing=3>

  <tr>

    <td id=cell_1><input type=text id=input_1 form=game_form value=x></td>

    <td id=cell_2><input type=text id=input_2 form=game_form></td>

    <td id=cell_3><input type=text id=input_3 form=game_form></td>

  </tr>

  <tr>

    <td id=cell_4><input type=text id=input_4 form=game_form></td>

    <td id=cell_5><input type=text id=input_5 form=game_form></td>

    <td id=cell_6><input type=text id=input_6 form=game_form></td>

  </tr>

  <tr>

    <td id=cell_7><input type=text id=input_7 form=game_form></td>

    <td id=cell_8><input type=text id=input_8 form=game_form></td>

    <td id=cell_9><input type=text id=input_9 form=game_form></td>

  </tr>

</table>

Javascript

$(window).load(

    function checkInput() {

//        alert(I am an alert box!1);

        var cell = document.getElementById('input_1');

        alert(cell.value);

        **document.getElementById('input_1').onchange**(

            doSomething()

        );

    }

);





function doSomething(){

    alert(I am an alert box!2);



}