jquery data selector

Question

At the moment I'm selecting like this:

$('a[data-attribute=true]')

Which seems to work just fine, but it would be nice if jQuery was able to select by that attribute without the 'data-' prefix.

I haven't tested this with data added to elements via jQuery dynamically, so that could be the downfall of this method.

I've created a new data selector that should enable you to do nested querying and AND conditions. Usage:

$('a:data(category==music,artist.name==Madonna)');

The pattern is:

:data( {namespace} [{operator} {check}]  )

"operator" and "check" are optional. So, if you only have :data(a.b.c) it will simply check for the truthiness of a.b.c.

You can see the available operators in the code below. Amongst them is ~= which allows regex testing:

$('a:data(category~=^mus..$,artist.name~=^M.+a$)');

I've tested it with a few variations and it seems to work quite well. I'll probably add this as a Github repo soon (with a full test suite), so keep a look out!

The code:

(function(){

    var matcher = /\s*(?:((?:(?:\\\.|[^.,])+\.?)+)\s*([!~><=]=|[><])\s*("|')?((?:\\\3|.)*?)\3|(.+?))\s*(?:,|$)/g;

    function resolve(element, data) {

        data = data.match(/(?:\\\.|[^.])+(?=\.|$)/g);

        var cur = jQuery.data(element)[data.shift()];

        while (cur && data[0]) {
            cur = cur[data.shift()];
        }

        return cur || undefined;

    }

    jQuery.expr[':'].data = function(el, i, match) {

        matcher.lastIndex = 0;

        var expr = match[3],
            m,
            check, val,
            allMatch = null,
            foundMatch = false;

        while (m = matcher.exec(expr)) {

            check = m[4];
            val = resolve(el, m[1] || m[5]);

            switch (m[2]) {
                case '==': foundMatch = val == check; break;
                case '!=': foundMatch = val != check; break;
                case '<=': foundMatch = val <= check; break;
                case '>=': foundMatch = val >= check; break;
                case '~=': foundMatch = RegExp(check).test(val); break;
                case '>': foundMatch = val > check; break;
                case '<': foundMatch = val < check; break;
                default: if (m[5]) foundMatch = !!val;
            }

            allMatch = allMatch === null ? foundMatch : allMatch && foundMatch;

        }

        return allMatch;

    };

}());

You can also use a simple filtering function without any plugins. This is not exactly what you want but the result is the same:

$('a').data("user", {name: {first:"Tom",last:"Smith"},username: "tomsmith"});

$('a').filter(function() {
    return $(this).data('user') && $(this).data('user').name.first === "Tom";
});

I want to warn you that $('a[data-attribute=true]') doesn't work, as per Ashley's reply, if you attached data to a DOM element via the data() function.

It works as you'd expect if you added an actual data-attr in your HTML, but jQuery stores the data in memory, so the results you'd get from $('a[data-attribute=true]') would not be correct.

You'll need to use the data plugin http://code.google.com/p/jquerypluginsblog/, use Dmitri's filter solution, or do a $.each over all the elements and check .data() iteratively

There's a :data() filter plugin that does just this :)

Some examples based on your question:

$('a:data("category=music")')
$('a:data("user.name.first=Tom")');
$('a:data("category=music"):data("artist.name=Madonna")');
//jQuery supports multiple of any selector to restrict further, 
//just chain with no space in-between for this effect

The performance isn't going to be extremely great compared to what's possible, selecting from $._cache and grabbing the corresponding elements is by far the fastest, but a lot more round-about and not very "jQuery-ey" in terms of how you get to stuff (you usually come in from the element side). Of th top of my head, I'm not sure this is fastest anyway since the process of going from unique Id to element is convoluted in itself, in terms of performance.

The comparison selector you mentioned will be best to do in a .filter(), there's no built-in support for this in the plugin, though you could add it in without a lot of trouble.

You can set a data-* attribute on an elm using attr(), and then select using that attribute:

var elm = $('a').attr('data-test',123); //assign 123 using attr()
elm = $("a[data-test=123]"); //select elm using attribute

and now for that elm, both attr() and data() will yield 123:

console.log(elm.attr('data-test')); //123
console.log(elm.data('test')); //123

However, if you modify the value to be 456 using attr(), data() will still be 123:

elm.attr('data-test',456); //modify to 456
elm = $("a[data-test=456]"); //reselect elm using new 456 attribute

console.log(elm.attr('data-test')); //456
console.log(elm.data('test')); //123

So as I understand it, seems like you probably should steer clear of intermingling attr() and data() commands in your code if you don't have to. Because attr() seems to correspond directly with the DOM whereas data() interacts with the 'memory', though its initial value can be from the DOM. But the key point is that the two are not necessarily in sync at all.

So just be careful.

At any rate, if you aren't changing the data-* attribute in the DOM or in the memory, then you won't have a problem. Soon as you start modifying values is when potential problems can arise.

Thanks to @Clarence Liu to @Ash's answer, as well as this post.

$('a[data-category="music"]')

It works. See Attribute Equals Selector [name=”value”].