Disable backspace and delete key with javascript in IE

Question

Anyone know how can I disable backspace and delete key with Javascript in IE? This is my code below, but seems it's not work for IE but fine for Mozilla.

onkeydown="return isNumberKey(event,this)"

function isNumberKey(evt, obj)
{

    var charCode = (evt.which) ? evt.which : evt.keyCode
    if (charCode == 8 || charCode == 46) return false;

    return true;
}

Answer 1

This code cancels backspace action.

window.onkeydown = function (event) {

    if (event.which == 8) { 

         event.preventDefault();   // turn off browser transition to the previous page 

                 // put here code you need 

        }; 

};