Grab the ID of a SPAN tag and add some value to a Text Box Field according to which tag has been clicked

Question

I was trying to grab the ID of the SPAN tag when a user clicked it.
Since the ID of each tag contains two digits, they would be used for referring
to the value of their corresponding hidden text box field,
but I am stuck over this question.

Here is part of the code that I have written.
I need your help to finish it because I don't know how to move on.

<script type="text/javascript">
    $(document).ready(function(){ 
           $("#^=content").click(function(event){
        // var digit = extract the last two digit of the id
           var id_of_the_hidden_field = "hidden"+digit;
           $("#show").val()=$("#hidden").val();
            });
        });
</script>
<div id="test22">
<span id="content22">Click to add the value</span>
<input type="hidden" id="hidden22" value="hello">
</div>

<div id="test33">
<span id="content33">Click to add the value</span>
<input type="hidden" id="hidden33" value="world">
</div>

<input type="text" id="show">

Answer 1

It would look like this:

$("[id^=content]").click(function(event){
  $("#show").val($("#" +   this.id.replace('content', 'hidden')).val());
});​

You can test it here. There are a few corrections to this, first you need an attribute starts-with selector ([attr^=value]) to find the elements by ID (though you could give the spans a class and use .class as well). Then we're using the ID, replacing 'content' with 'hidden' via string.replace() and grabbing input element by that ID. Also when setting a value use .val(value), .val() = value isn't valid :)

If the structure is consistent you can make this much simpler, by relying on the fact that the <input type="hidden" /> is beside the <span> like this:

$("[id^=content]").click(function(event){
    $("#show").val($(this).next().val());
});​

You cant test it here

---

As I said in the first example, if adding classed in an option it will makes your life easier, here's a version doing that:

<div id="test22">
  <span id="content22" class="clickable">Click to add the value</span>
  <input type="hidden" id="hidden22" value="hello">
</div>    
<div id="test33">
  <span id="content33" class="clickable">Click to add the value</span>
  <input type="hidden" id="hidden33" value="world">
</div>    
<input type="text" id="show">​​​​​​

and the jQuery:

$(".clickable").click(function(event){
  $("#show").val($(this).next().val());
});​

Here's that version in a demo

Answer 2

or

 var digit = $(this).attr(id).substring(7, 9);