Question

If in a webkit browser like Chrome i do:

$$('span');

I get a result that looks almost exactly the same as jQuery’s:

$('span');

---

If in the console I look for definition of $$ I get:

bound: function ()
{
    return document.querySelectorAll.apply(document, arguments)
}

And for $ I get:

function (a,b){return new c.fn.init(a,b)}

---

What type of functions can I do on a $$ object that I cannot really do with a jQuery ($) object?

Answer 1

Since $$ is just a wrapper for querySelectorAll, you can pass any valid selectors.

“What type of functions can I do on a $$ object that I cannot really do with a jQuery ($) object?”

First, $$ isn’t an object like jQuery. It is an object, but it’s just a simple function object that is a wrapper (shortcut) for document.querySelectorAll. It returns a NodeList of the elements it found.

The only thing it supports that Sizzle doesn’t specifically support, to my knowledge, is :nth-of-type.

(Of course Sizzle defaults to qsa when you give a valid selector, so you can pass nth-of-type to the jQuery function in browsers that also support qsa.)

With Sizzle, there are several selectors that are not supported by querySelectorAll, so you can technically do more with jQuery/Sizzle.

Those include:

• :eq()
• :gt()
• :lt()
• :first
• :last
• :not() (When you give it multiple selectors. Simple :not() values are supported in qsa.)
• :animated
• :input
• :button
• :checkbox
• :even
• :odd
• :has()
• :image
• :password
• :radio
• :reset
• :selected
• :submit
• :text
• :visible

…to name a few several.

---

Keep in mind that Sizzle first tries to use querySelectorAll. If you passed a proprietary selector, it then defaults to Sizzle’s own engine.

Since qsa is typically faster than Sizzle, it may be advisable to consider alternatives to the proprietary selectors listed above in order to improve performance.

---

Also note that Webkit does not define $$ anywhere except for in the console. the $$ shortcut is not available in your scripts unless you make it available.