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LeeMobile
LeeMobile

Reputation: 3825

HTML Classes WITH IDs

I'm a little confused about HTML classes and IDs, as I'd like to use them BOTH to describe an HTML element. Is this valid and supported by most browsers?

The motivation for me to use both is this:

  1. I have a CSS style that I would like applied to multiple elements.
  2. I have some AJAX and Javascript that will manipulate those same elements, so I need a way to identify which element is which using an ID.
  3. So I'd like to use an id to identify each element for JS manipulation AND at the same time I would like to specify a class so that the same style is applied from the same css.

Upvotes: 4

Views: 341

Answers (6)

Iralda Mitro
Iralda Mitro

Reputation: 7356

Yes it is valid in all browsers. ID expresses just the unique IDentification of your html control through others, and class applies some style to it. Use IDs when there is only one occurence per page. Use classes when there are one or more occurences per page.

Upvotes: -3

AmbroseChapel
AmbroseChapel

Reputation: 12087

Just a very obscure note about combining class and id in your CSS declarations, there's a bug with IE6, if you have:

  • two or more pages which have an element with the same id

  • those elements have different classes

  • you're styling them using an #idname.classname rule

then only the first rule in the stylesheet will take effect.

See this page for details

Upvotes: 0

Tom
Tom

Reputation: 5835

You can definitely use both if you need to.

An ID is typically used to identify structural sections of your site - you should have only one element with a particular ID and any element can have only one ID.

A class is used to set styles which might be used in more than one place in your HTML file - any element can have multiple classes set.

A typical HTML document using both IDs and classes might be something like

<html>
...
<body>
<div id="header"></div>
<ul id="nav" class="full-width dark">...</ul>
<div id="content">
<div id="important-container" class="class-set-by-javascript another-class-set-by-javascript"></div>
</div>
</body>
</html>

Upvotes: 2

Arve Systad
Arve Systad

Reputation: 5479

Yes, it is perfectly valid to use both the ID and Class properties in one element. Example:

<div class="infoBox" id="myUniqueStyle"> *content* </div>

Still, keep in mind that an ID can only be used once (hence its name), while you can use classes as many times as you'd like througout a document. You can still use both the ID and the class to apply styles, while only the ID is a simple way of reaching the element through javascript.

A good way of doing it is applying IDs to all elements that you know are unique (header, navigation, main containers etc.), and classes to everything else.

"Is the" applies to elements using ID: "This is the navigation bar", "this is the header"

"Is a" or "is an" applies to elements using classes: "This is a blogPost", "this is an infoBox" etc.

Upvotes: 7

SirDemon
SirDemon

Reputation: 1758

Yes, any normal browser should allow the setting of CSS classes regardless of element id. However, setting styles on a specific element (using ids, for example) may override styles set through a CSS class.

Upvotes: 0

Chris Bartow
Chris Bartow

Reputation: 15111

An ID would be unique to only one item, where a class can be used to group many items together. You can use them together as you stated, ID as a unique identifier for Javascript and the class to markup with CSS.

Search for html class vs id to get many articles about this topic.

Example:

<ul>
    <li class="odd" id="item1">First Item in the List</li>
    <li class="even" id="item2">Second Item in the List</li>
    <li class="odd" id="item3">Third Item in the List</li>
</ul>

Upvotes: 8

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