Does jQuery have an equivalent to Prototype's Element.identify?

Question

Is there a built in method or defacto default plugin that will let you automatically assign an unique ID to an element in jQuery, or do you need to implement something like this yourself? I'm looking for the jQuery equivalent to Prototype's identify method

Here's an example. I have some HTML structure on a page that looks like this

<span id="prefix_1">foo bar</span>
...
<div id="foo">
   <span></span>
   <span></span>
   <span></span>
</div>

I want to assign each of the spans an ID that will be unique to the page. So after calling something like this

$('#foo span').identify('prefix');   //fake code, no such method

The rendered DOM would look something like this

<span id="prefix_1">foo bar</span>
...
<div id="foo">
   <span id="prefix_2"></span>
   <span id="prefix_3"></span>
   <span id="prefix_4"></span>
</div>

Is there anything official-ish/robust for jQuery, or is this something most jQuery developers roll on their own?

Answer 1

jQuery.fn.identify = function(prefix) {
    var i = 0;
    return this.each(function() {
        if(this.id) return;
        do { 
            i++;
            var id = prefix + '_' + i;
        } while($('#' + id).length > 0);            
        $(this).attr('id', id);            
    });
};

$('span').identify('test');

Tested this on:

<span id='test_2'></span>
<span>test1</span>
<span>test2</span>
<span>test3</span>

Turned it to:

<span id="test_2"></span>
<span id="test_1">test1</span>
<span id="test_3">test2</span>
<span id="test_4">test3</span>

Answer 2

Not that I know of, but you could do this yourself by adding the id attribute and supplying a GUID.

To add the attribute:

$(foo).attr( "id", createGuid() );

For the createGuid() implementation, see this question.

Note that you could easily turn this into a jQuery plug-in so that this function (you could even name it identify()) is available on any $-expression.

Answer 3

Based on Paolo's solution:

jQuery.fn.identify = function(prefix) {
    var i = 0;
    return this.each(function() {
        if($(this).attr('id')) return;
        do { 
            i++;
            var id = prefix + '_' + i;
        } while($('#' + id).length > 0);            
        $(this).attr('id', id);            
    });
};

$('span').identify('test');

A small change that will avoid to re-count already used ids.

Answer 4

I'd modify the given function slightly and make it:

jQuery.fn.identify = function(prefix) {
    var i = 0;
    return this.each(function() {
        if($(this).attr('id')) return;
        do { 
            i++;
            var id = prefix + '_' + i;
        } while(document.getElementById(id) != null);            
        $(this).attr('id', id);            
    });
};

ID's could contain special characters that would require escaping in order to work properly with jQuery's CSS selector engine--like ".". So instead of finding them and escaping them, it's simpler and faster to replace it with the document method.