append attributes to input element using jquery

Try this:

$("#Requester_Value").attr("data-val-required","The Requested value field is required.");
$("#Requester_Value").attr("data-val-number","The field Requester must be a string.")

You can use .attr() to get set attribute value:

$('#Requester').attr({'data-val-required':'The Requested value field is required.' ,'data-val-number':'The field Requester must be a string.'});

.attr() with data-* will set the data property as well as attribute value for that element. whereas .data() will only set data property internally and values wont be reflected in attributes.

You can use .attr() to set an attribute of an element, see the jQuery documentation here

    $('#Requester_Value').attr("data-val-required","The Requested value field is required.");

Ok if you want to add this data to input then put your input in container such div and use this method

var $div = $('div');

var spltInp = $div.html().split(' ');

var i = Math.floor(spltInp.length / 3);

var srt = spltInp.splice(i, 0, 'data-val-required="The Requested value field is required." data-val-number="The field Requester must be a string." ');

var newHtm = spltInp.join(' ');

$div.append(newHtm).children().eq(0).remove();

https://jsfiddle.net/L2roc4ka/

First split() html inside the div (input) then, use some number between array length (i) to avoid putting attr outside the input , and use this number as starting point to index the attr by splice(), finally convert the array to string by join()and append it to your div then remove the old one.

note : avoid using multi classes if you going to use this trick cause it may lead to syntax error and instead put those classes in another container like section and style it or avoid using this one.