For x in JavaScript

If you're new to Javascript/Actionscript/ECMAScript you might think there is a difference between objects (maps) and arrays, but there isn't. An array is simply a map (object) with the properties 0, 1, 2 etc. set to specific values.

This will list the properties of the map (0, 1, 2):

var a = ['a', 'b', 'c'];

for( i in a ) { console.log( i ); }

This will list the values of those properties:

var a = ['a', 'b', 'c'];

for( i in a ) { console.log( a[i] ); }

I find it surprising that javascript gets so much traction as a hidden jewel when really it's a pretty poor language compared to python, for instance. It started off being pooh-poohed (including by myself) by those who thought that it was some sort of cut-down 'scripting language' version of Java. Then Douglas Crockford pointed out that you could do closures in Javascript and it became kind of cool to praise Javascript. When I started using it (after programming in C, C++, Lisp, Java, Python, etc.) I discovered an interesting language but too many pain points (after the joy of python coding) to consider it anything special.