jQuery.map( arguments, fn ) can fail in Safari

[spicyj]

The "isArray" heuristic looks at elems[ 0 ] and elems[ elems.length - 1 ]; if they are both truthy; it assumes that elems is an array. In the case that one of the two elements is falsey, map will treat it as an object instead of an array.

Normally, that's pretty much okay, but in Safari, for ( key in arguments ) seems to yield no values. This page demonstrates the bug:

​http://jsfiddle.net/qeSxC/

By testing the two end values for undefined instead of truthiness, everything is fixed. Patch and a test on GitHub:

​https://github.com/spicyj/jquery/commit/204844c8d7acd97d20b3add013156b1a2cc58c3c

[spicyj]

JSLint didn't like my line breaks. Happier patch:

​https://github.com/spicyj/jquery/commit/1efda53b4fe213e372d31f8bf2e04cba49a795a9

[Rick Waldron]

Without arguing the semantics of jQuery.map's first argument, you're using it like "each" which is incorrect - jQuery.map should not be used for side-effects. jQuery.map is expected to return a mutated copy of the original array or object argument. I've reduced the test case further to show the correct usage: ​http://jsfiddle.net/rwaldron/FU7Fv/

[spicyj]

My bug stands. Screenshot from your fiddle:

​http://uploads.hipchat.com/6574/26709/u3mhjt5gjugeigk/upload.png

(In my original script, I was using jQuery.map properly but changed it to run console.log for that demo.)

[spicyj]

If you prefer to relying on jQuery.map's each-like functionality, you can use this patch instead which uses map "properly" in the test case:

​https://github.com/spicyj/jquery/commit/81e0e8cd42da0dc93d2d69cd8bed6915105d1d0b

[Rick Waldron]

Reopening for further discussion

[Robert Katić]

This would be a duplicate of #9025 (that is wrongly declared as a duplicate) that already has a patch.

[addyosmani]

Duplicate of #9025.