jQuery bug with FireFox: z.indexOf is not a function

tomo — Wed, 02 Feb 2011 12:05:43 +0000

I've tracked down a source of the bug which breaks jquery (1.2.6) in FireFox (Chrome is fine) where you'll see a debug message of "z.indexOf is not a function". If you're running a minified jquery then the line number won't help locate the bug, but in this case it was around line 1715:

type == "^=" && z && !z.indexOf(m[5])

This code is triggered by jquery attribute filters like ^= (starts with) or *= or ~= and in this case I found that if z had been 0 then the code which checks "&& z" would short circuit and not try to reference indexOf of z.

Looking deeper, I found that z == -1 (not a string) and that this was because I was filtering on the 'value' attribute, and that in FireFox, the 'li' node was being given some value of -1. You can check this by running "$('li')" and checking out the returned values. In Chrome, there is no value. This difference causes a bug in FireFox.

One workaround is to use only use attribute filters when using selectors that select for specific tags which exclude 'li', at least for filtering on 'value'. For example, use 'input[value^=whatever]' instead of just '[value^=whatever]'.

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jQuery bug with FireFox: z.indexOf is not a function