Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
312 views
in Technique[技术] by (71.8m points)

What does it mean in HTML 5 when an attribute is a boolean attribute?

What does it mean when an attribute like the hidden attribute is a boolean attribute? Can someone explain this in layman's terms?

Question&Answers:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

As already stated boolean attributes are attributes that are evaluated either true or false.

However, from HTML5 Spec - http://www.w3.org/TR/html5/infrastructure.html#boolean-attributes

2.5.2 Boolean attributes

A number of attributes are boolean attributes. The presence of a boolean attribute on an element represents the true value, and the absence of the attribute represents the false value.

If the attribute is present, its value must either be the empty string or a value that is an ASCII case-insensitive match for the attribute's canonical name, with no leading or trailing whitespace.

The values "true" and "false" are not allowed on boolean attributes. To represent a false value, the attribute has to be omitted altogether.

Note that this means that <div hidden="true"> is not allowed in HTML5.

Correct would be either <div hidden> or <div hidden=""> or <div hidden="hidden"> or case-insensitive and single quotes/unquoted variations of any of them.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...