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.

Answer 5

With this code you can override the "get" and "set" of .val() for specific elements:

(function () {

    var __val = $.fn.val;
    $.fn.val = function (value) {
        if (this[0] && (this[0].$val_get || this[0].$val_set)) {
            if (arguments.length === 0) return this[0].$val_get();
            else return this[0].$val_set(value) || this;
        }
        return __val.apply(this, arguments);
    };

})();

Now you have to create two function properties on the DOM element - $val_get and $val_set:

<input type="text" id="myInput" />
<input type="text" id="someOtherInput" />

<script>

    $('#myInput')[0].$val_get = function () {
        console.log('Got value from myInput!');
        return this.value;
    };

    $('#myInput')[0].$val_set = function (value) {
        console.log('Set value of myInput!');
         this.value = value;
    }

    //----

    $('#myInput').val('Hello!'); //Console: "Got value from myInput!"
    $('#myInput').val(); //Hello! | Console: "Set value to myInput!"

    $('#someOtherInput').val('Hello!'); //Console: ""
    $('#someOtherInput').val(); //Hello! | Console: ""

</script>

This is useful for creating components that orchestrate multiple controls.

JsFiddle: https://jsfiddle.net/oj4gt2ye/6/

Answer 6

I have something to add to CMS answer, my implementation would differ and be like this:

(function ($) { var fnVal = $.fn.val;
    $.fn.val = function(value) {
        if (typeof value == 'undefined') {
            return fnVal.call(this);
        }
        var result = fnVal.call(this, value);
        $.fn.change.call(this);
        // here you can add some more implementation
        return result;
    };
})(jQuery);

observe the $.fn.change.call(this); will be called before exiting the val('') function this will trigger also the .change() on each val('') assignment.