[jquery] jquery function val() is not equivalent to "$(this).value="?

When I try to set a text input to blank (when clicked) using $(this).value="", this does not work. I have to use $(this).val('').

Why? What is the difference? What is the mechanism behind the val function in jQuery?

$(document).ready(function() {
    $('#user_name').focus(function(){
        $(this).val('');
    });
});
// error code: not working...
$(document).ready(function() {
    $('#user_name').focus(function(){
        $(this).value='';
    });
});

One thing you can do is this:

$(this)[0].value = "Something";

This allows jQuery to return the javascript object for that element, and you can bypass jQuery Functions.

$(this).value is attempting to call the 'value' property of a jQuery object, which does not exist. Native JavaScript does have a 'value' property on certain HTML objects, but if you are operating on a jQuery object you must access the value by calling $(this).val().

Note that :

typeof $(this) is JQuery object.

and

typeof $(this)[0] is HTMLElement object

then : if you want to apply .val() on HTMLElement , you can add this extension .

HTMLElement.prototype.val=function(v){
   if(typeof v!=='undefined'){this.value=v;return this;}
   else{return this.value}
}

Then :

document.getElementById('myDiv').val() ==== $('#myDiv').val()

And

 document.getElementById('myDiv').val('newVal') ==== $('#myDiv').val('newVal')

????? INVERSE :

Conversely? if you want to add value property to jQuery object , follow those steps :

1. Download the full source code (not minified) i.e: example http://code.jquery.com/jquery-1.11.1.js .

2. Insert Line after L96 , add this code value:"" to init this new prop

3. Search on jQuery.fn.init , it will be almost Line 2747

4. Now , assign a value to value prop : (Before return statment add this.value=jQuery(selector).val())

Enjoy now : $('#myDiv').value