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What’s new in CSS 4 selectors

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What’s new in CSS 4 selectors

· Web Dev Zone ·
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The following are the highlights of what is new in CSS 4 selectors:

  • Determining the subject of a selector. Currently, if a selector consists of several compound selectors, the last one is considered its subject. The subject determines what elements the rule applies to. CSS 4 allows one to make any compound selector the subject, by prepending a dollar sign. For example:
    $ul li:hover {
        color: green;
    }
    Here, if one hovers over a list element, the whole list will turn green. This is a great and dearly needed feature.

  • Pseudo-class :nth-match(). Lets you apply a rule to every n-th match for a given selector list.
    :nth-match(an+b of selector-list)
    Previously, you could only access every n-th child. This selector gives you more flexibility.

  • UI states pseudo-classes allow you to style elements depending on their user interface state. Examples: :disabled, :checked (radio elements, checkbox elements, menu items, etc.), :in-range (for input elements with range limitations).

  • The matches-any pseudo-class :matches(). Example:
    :matches(section, article, aside) h1 {
        font-size: 3em;
    }
    
    The above selector is an abbreviation for
    section h1, article h1, aside h1
    

  • The contextual reference element pseudo-class ‘:scope’. When you use selectors to query for elements, you can start your search in a list of elements that is iterated over, one element at a time. :scope is a placeholder for the current element. Example:
    document.querySelector(":scope > ul > li", elems)
    
    The above returns all list items that are direct children of unordered lists that are direct children of the elements in elems.

More details (partial source of this post): “Discover What’s New in CSS 4 [selectors]” by Scott Gilbertson for Webmonkey.

 

Source: http://www.2ality.com/2011/12/css4-selectors.html

Deploying code to production can be filled with uncertainty. Reduce the risks, and deploy earlier and more often. Download this free guide to learn more. Brought to you in partnership with Rollbar.

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