Inline javascript, what is the 'javascript' in 'javascript:alert('asdf')'

Question

I don't write inline javascript, but I see and work with it all the time in code bases that I work with:

<div onClick='javascript:alert("asdf");'></div>

I did some tests and found that in all my browsers, even IE in IE5 mode, you can change javascript to literally anything, and the alert will fire just fine.

<div onClick='qwerty:alert("asdf");'></div>

What is that delimiter? What is the history behind it? Is it ever needed or useful? I seem to remember that <script type="text/javascript"> doesn't really need the type attribute set, is that related to this, as well? I tried some googling around, but it's hard to search for.

I believe this answers half your question: http://programmers.stackexchange.com/a/62118 — Dave, Mar 13 '13 at 22:40

score 6 · Accepted Answer · edited May 23 '17 at 12:11

6

It is a label that is ONLY needed in IE if the first script on the page is VBScript
If you add <script type="VBScript"></script> to (older?) IEs your later scripts will fail if they are javascript specific and do not have the label javascript: to tell IE to switch back

See my answer here: What does the JavaScript pseudo protocol actually do?

edited May 23 '17 at 12:11

Community

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answered Mar 13 '13 at 22:40

mplungjan

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so i can put any word i want and it 'll work on any browser?? – ebram khalil Mar 13 '13 at 22:43
Yes. It is treated as a label – mplungjan Mar 13 '13 at 22:43
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But while you *can* put any word there, doing so it nonsense (unless you are going to break or continue from a loop), so don't put anything there. – Quentin Mar 13 '13 at 22:48

score 2 · Answer 2 · edited May 23 '17 at 11:50

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In general it's simply a label, analogous to:

label:
  statement;

Which is why qwerty:alert("asdf") works because it is legal Javascript.

IE does handle this differently; you can find more details in this answer.

Inline javascript, what is the 'javascript' in 'javascript:alert('asdf')'

2 Answers2