for each in:

JAVASCRIPT:

1. for each (var item in [1, 2, 3]) alert(item);

JavaScript 1.6 added the Array.forEach method:

JAVASCRIPT:

1. [1, 2, 3].forEach(function(item) { alert(item) });

JavaScript 1.7 added array comprehensions for array initialization:

JAVASCRIPT:

1. var squares = [item * item for each (item in [1, 2, 3])];

I just realized I can (ab)use comprehensions to iterate arrays with Perl-like syntax by throwing away the result:

JAVASCRIPT:

1. [alert(item) for each (item in [1, 2, 3])];

I can iterate object properties the same way:

JAVASCRIPT:

1. var obj = { foo: 1, bar: 2, baz: 3 };
2. [alert(name + "=" + obj[name]) for (name in obj)];

Edward Lee points out how to use Iterators:

JAVASCRIPT:

1. [alert(key + "=" + val) for ([key, val] in Iterator({a:1,b:2,c:3}))]