javascript - Adding Keypress/keydown event on dynamic html

I have the following dynamic input html in my project

  $(this).html("");

Now i was trying to add validation for using only numeric in above input text field.

But being new to jquery i was wondering how do i add keypress event to it

Want to use following validation to it

function isNumber(evt) {

    evt = (evt) ? evt : window.event;
    var charCode = (evt.which) ? evt.which : evt.keyCode;
    if (charCode > 31 && (charCode < 48 || charCode > 57)) {
        return false;
    }
    return true;
}

I tried follwoing but does not seem to work

$(this).html("");

EDIT

Any other way to add validation for using only number