Edit in JSFiddle

<input id="id_price" type="number" min=0 />
<script type="text/javascript">
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;
}
document.getElementById('id_price').setAttribute("onkeypress", "return isNumber(event)");
</script>