WP-UI breaks Array.indexOf

WP-UI is monkey patching Array.indexOf with a bad/invalid implementation.

http://plugins.trac.ww.wp.xz.cn/browser/wp-ui/trunk/js/wp-ui-dev.js#L1109

This breaks other scripts! At the very least, this implementation should return -1 when a match is not found, not undefined. But if you’re going to monkey patch, do it right. Mozilla provides a fully standards-compliant implementation here:

https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Array/indexOf#Compatibility

http://ww.wp.xz.cn/extend/plugins/wp-ui/