Can someone tell me what exactly the two above lines of javascript do? And more importantly, what it's called so I can search some javascript references to learn about it? I assume they are both creating some form of an array that objects can be added to...?
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Curly braces are syntax for creating a Javascript object (which is really a glorified collection of key/value pairs); the brackets make a resizable array.
These are called literals, and they're a handy shortcut to help you make objects and arrays without a lot of typing (good, because you use them all the time). Many other programming languages have similar literal syntax for maps and arrays.
J Cooper
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It creates an empty dictionary in map and an empty array in list.
Read up on these structures at http://www.geocities.com/schools_ring/ArrayAndHash.html.
Sophie Alpert
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Your link calls javascript objects hash tables, you call them dictionaries. Just call them objects - calling them something else is misleading at best - see http://stackoverflow.com/questions/368280/javascript-hashmap-equivalent#383540 – Christoph Jan 06 '09 at 10:57