开发商为何分裂

Question

I see so many things like this: S = "<scr" + "ipt language=\\"JavaScript1.2\\">\\n<!--\\n";

Why do they do this, is there an application/browser that messes up if you just use straight "<script>" ?

Answer 1

Have a look at this question:

Javascript external script loading strangeness.

Taken from bobince's answer :

To see the problem, look at that top line in its script element:

 <script type="text/javascript"> document.write('<script src="set1.aspx?v=1234" type="text/javascript"></script>'); </script>

So an HTML parser comes along and sees the opening <script> tag. Inside <script>, normal <tag> parsing is disabled (in SGML terms, the element has CDATA content). To find where the script block ends, the HTML parser looks for the matching close-tag </script>.

The first one it finds is the one inside the string literal. An HTML parser can't know that it's inside a string literal, because HTML parsers don't know anything about JavaScript syntax, they only know about CDATA. So what you are actually saying is:

 <script type="text/javascript"> document.write('<script src="set1.aspx?v=1234" type="text/javascript"> </script>

That is, an unclosed string literal and an unfinished function call. These result in JavaScript errors and the desired script tag is never written.

A common attempt to solve the problem is:

 document.write('...</scr' + 'ipt>');

This wouldn't explain why it's done in the start tag though.

Answer 2

The more appropriate way to append scripts is to use the DOM.

1. Create an element of type <script> . See documentation for document.createElement .
2. Set its attributes ( src , type etc.)
3. Use body.appendChild to add this to the DOM.

This is a much cleaner approach.