onclick or onClick?

Solution 1:

Because some browsers (depending on the DOCTYPE) are tolerant of the inline onClick="something();" attribute...it seems to have spread a bit, even into JavaScript questions where it doesn't work, since case matters.

Also, specifically to stackoverflow...people using it in questions...well, most of the time they wouldn't be asking a question if their code worked :)

Solution 2:

@Nick Craver pretty much has it nailed down and has my vote; I just wanted to add my thought.

I think it's onClick is often used in conversation because it's a bit more readable, and as an old habit from those of us who predate all lowercase HTML. However, in code - both JavaScript and HTML, onclick is correct and the only way it should appear. Even if you're using an older HTML doctype, stick to lowercase. If you ever update to a more strict doctype, you'll be glad your code doesn't need to be checked for case.

Solution 3:

It's just that for most browsers HTML attributes are case insensitive, but JS is case-sensitive. onClick will work in html, but if you're defining the handler in JS, you need to use the lowercased onclick.