What is the real reason that we must escape a forward slash in a JavaScript string, and also why must we escape string/no string in XHTML. A lot of tutorials just brush over this issue.
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3 Answers
What is the real reason that we must escape a forward slash in a JavaScript string
In an HTML 4 document, the sequence </ inside an element defined as containing CDATA (such as script) is an end tag and will end the element (with an error if it is not </script>.
As far as JS is concerned / and \/ are identical inside a string. As far as HTML is concerned </ starts an end tag but <\/ does not.
, and also why must we escape string/no string in XHTML.
XHTML doesn't provide a method of specifying that an element intrinsically contains CDATA, so you need to explicitly handle characters which would otherwise have special meaning (<, &, etc). Wrapping the contents of the element with CDATA markers is the easiest way to achieve this.
4 Comments
rubixibuc
So we never have to escape a single forward slash, only a </ ? whether it is XHTML inside a string or outside a string? Thanks :-)
rubixibuc
In other words in XHTML when must we escape a forward slash?
Quentin
In "normal" XHTML (which nobody uses), never. In HTML-compatible XHTML (which everybody who wants IE 8 and lower to be supported uses), the same places as in HTML.
Sz.
So, @rubixibuc, to recap, and make it clear: "So we never have to escape a single forward slash, only a </ ?". Correct.
You don't need to escape / in a JavaScript string, just \, because if you don't, then the string yes\no will inadvertently be transformed into yes<newline>o. Escaping the \ will prevent that.
Also, if you don't escape & in a URL, then whatever comes after it will be considered a new parameter. For example, a=Q&A will mean "the parameter a has the value "Q" and there's also a parameter A" instead of "the parameter a has the value "Q&A"". The correct way of escaping that would be a=Q%26A.
2 Comments
Paŭlo Ebermann
Why would you write
yes\no for the prompt?
rid
@Paŭlo, you probably wouldn't, that's the best example of unintended use I could come up with.
The slash is needed to prevent browsers, particularly older ones, to erroneously interpret the forward slash as a closing JavaScript marker.
2 Comments
Quentin
There is nothing erroneous about it.
Bozhidar Stoyneff
@Quentin, of course, it's erroneous. While in a string mode, the special for the interpreter characters are just characters...