Override jQuery .val() function?

Question

Is there a way to easily override jQuery's val() function?

The reason I want to override it is that I want to add some processing each time a value is set for an element. And I don't want to make another custom value setter, such as myVal().

Answer 1

You can store a reference to the original val function, then override it and do your processing, and later invoke it with call, to use the right context:

(function ($) {
  var originalVal = $.fn.val;
  $.fn.val = function(value) {
    if (typeof value != 'undefined') {
      // setter invoked, do processing
    }
    return originalVal.call(this, value);
  };
})(jQuery);

Note that you can distinguish between a getter call $(selector).val(); and a setter call $(selector).val('new value'); just by checking if the value argument is undefined or not.

Answer 2

I know it's an old subject but it's first in google search and the answer is not completely right...

For example if you try in the console $('#myinput').val() you should get the value of #myinput.

But if you do $('#myinput').val(undefined) you should set the value of #myinput!( With the current answer and the comments of it, you will not set the value of #myinput)

Here is an upgraded answer that use arguments.

(function ($) {
  var originalVal = $.fn.val;
  $.fn.val = function(value) {
    if (arguments.length >= 1) {
      // setter invoked, do processing
      return originalVal.call(this, value); 
    }
    //getter invoked do processing
    return originalVal.call(this);
  };
})(jQuery);

if you want to pass all the arguments you can also use apply

(function ($) {
  var originalVal = $.fn.val;
  $.fn.val = function(value) {
    if (arguments.length >= 1) {
      // setter invoked, do processing
    } else {
      //getter invoked do processing
    }
    return originalVal.apply(this, arguments);
  };
})(jQuery);

I hope it help!

Answer 3

I know the problem is old but just to give a full solution. In order for both the jQuery.val() and the jQuery.val(value) to work after override you need to override it properly and separately. Because when calling jQuery.val() then originalVal.call(this, value); will not work correctly.

To do it in a correct way you need to do something like that when getting the value: originalVal.call(this);

Here is a site where everything is explained: http://extremedev.blogspot.com/2012/01/override-jqueryval-and-jqueryvalvalue.html

Regards, Roman

Answer 4

If I am understanding you right, something like this should do the trick just fine:

jQuery.fn.val = function (new_val) {
    alert("You set a val! How wonderful!");
    this.value = new_val;
};

Just make sure you include the regular functionality: getting values of selects and so on. Just stick that code after after the regular jQuery library.