Unable to get data attribute value in jquery using PHP

I am working with Jquery and php,I have text box and i am trying to pass “data attribute” (data-vals) value using jquery but i am getting “undefined” as response, Here is my code,Where i am wrong ?

<input type='text' name='postcmnt' class='postcmnt' value='" + str + "' data-vals='123' onkeydown='search(this)' />
<script>
function search(ele) {
    if(event.key === 'Enter') {
            var valss=$(this).data('vals');
            alert('attribute value is '+valss); 
    }
}
</script>

Answer

Simply you can use on keypress with class postcmnt or with input

$('.postcmnt').on('keypress', function(e) {
    var code = e.keyCode || e.which;
    var _t = $(this);
    if(code==13){
        var valss=_t.data('vals');
        var inputVal=_t.val();
         alert('attribute value is '+valss);
         alert('input value is '+inputVal);
    }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<input type='text' name='postcmnt' class='postcmnt' value='abc' data-vals='123'/>