＆，＆，＆all在html中表现相似。 怎么样和为什么？

Question

P&G  
P&ampG  
P&G 

All these are same. Is the use of special entities only for javascript/url?

Answer 1

They do not mean the same thing.

P&G contains an undefined entity reference &G , as a validator would tell you. What browsers do with such references is that they are treated literally. If browsers start recognizing new entities, strange things may happen. And they are doing it now, since the added entities as per HTML5 drafts are being added. Incidentally, &G is not among them.

P&ampG is a quite similar case, except that some browsers with broken parsers might incorrectly take the &amp part as meaning the & character.

P&G is a correct notation that stands for P&G.

This has nothing to do with JavaScript, and nothing to do with URLs, any more than HTML document content in general. Ampersands are often needed in URLs, but this does not make the issue a question of URLs. JavaScript code is often written inside a script element, where special parsing rules may apply, depending on HTML version, but this depends on the content model of the element. (The style element is a similar case.)

Answer 2

For best results, you should always use the full form & . Period.

Well, except in environments that have a CDATA content type. In HTML, that would be elements like <script> , <style> , <xmp> , <listing> and so on. In XHTML, only in explicit CDATA blocks, delimited with <![CDATA[ .. ]]> .

If you do not write the reference out in full, not all browsers will display it the way you want, and you may get into trouble later if you inadvertently write things like "select&copy&paste".

Answer 3

No. Even HTML doesn't understand them and thus they are called Special Characters.

However, modern browsers correct that for you. (example of modern browsers correction):

Create a document with extension .htm|.html and save in the document after typing <h1>hi!</h1> . you will be able to see some heading. which should be wrong... (back to the topic)

There are hundreds of these little suckers. but main thing is, try to follow the standard as it:

1. helps your colleague understand your code better.
2. just because your browser lets you do this is old excuse.
3. you can fall into trouble without you even remembering how?
4. read about it in Complete Ref or http://www.w3schools.com/tags/ref_entities.asp

As a try writing <>10<20<> in browser, it will show you as it is if new modern browser, if old, who knows what would happen?