Confused with calling JQuery custom function

You'll need to return a seperate function for each element in the collection, normally done with return this.each ...

$.fn.cust = function () {
   return this.each(function() {
      $(this).click(function(e){
          alert($(this).val());
       });
   });
}

And value is not a valid attribute for a span element.

This should work better:

$.fn.cust = function () {
    $(this).click(function (e) {
        alert($(this).attr('val'));
    });
}

span does not have value.

http://jsfiddle.net/dREj6/

Also if you want to make your method chainable you should return an jQuery instance:

$.fn.cust = function () {
    return $(this).click(function (e) {
        alert($(this).attr('val'));
    });
}

$('span[rel*=comm]').cust().css('color', 'red');

http://jsfiddle.net/dREj6/1/

• rel are for links (anchor element) - use class
• use data attribute instead of custom attributes

http://jsbin.com/ogenev/1/edit

<span class='comm' data-val='12'>click</span>
<span class='comm' data-val='82'>click</span>

$.fn.cust = function(){

   $(this).click(function(){
      alert(this.dataset.val);
   });

};


$('.comm').cust();

It works if you use .attr('val')

$.fn.cust = function () {

    $(this).click(function(e){
      alert($(this).attr('val'));
    });
}
$('span[rel*=comm]').cust();

http://jsfiddle.net/fW7FT/

.val() is for input since they're the only one accepting the val attribute officialy

The call $('span[rel*=comm]') returns a JQuery wrapper for all spans matching the selector - the two ones you have in your example are picked both.

Now inside the definition of cust, $(this) refers to the wrapped array, which causes your issue. Use

$(this).each( function() { 
     $(this).click (...
});

Inisde each $(this) will point to each separate span element in the selection, so they will have the click handler individually attached and working as you expect.

You can achieve what you're looking for with this:

HTML:

<span rel='comm' val='12'>click</span>
<span rel='comm' val='82'>click</span>

JS:

var cust = function(source) {
  alert($(source).attr('val'));
}

$('span[rel*=comm]').click(function(e) {
 cust(this);
});

The JSFiddle working: http://jsfiddle.net/ejquB/