michael@0: // map.set(k, v) increments the map size iff map didn't already have an entry for k.
michael@0: 
michael@0: var m = Map();
michael@0: m.set('a', 0);
michael@0: assertEq(m.size, 1);
michael@0: m.set('a', 0);
michael@0: assertEq(m.size, 1);
michael@0: m.set('a', undefined);
michael@0: assertEq(m.size, 1);
michael@0: 
michael@0: m.set('b', 2);
michael@0: assertEq(m.size, 2);
michael@0: m.set('a', 1);
michael@0: assertEq(m.size, 2);