michael@0: // map.iterator() is live: entries added during iteration are visited.
michael@0: 
michael@0: var map = Map();
michael@0: function force(k) {
michael@0:     if (!map.has(k) && k >= 0)
michael@0:         map.set(k, k - 1);
michael@0: }
michael@0: force(5);
michael@0: var log = '';
michael@0: for (let [k, v] of map) {
michael@0:     log += k + ';';
michael@0:     force(v);
michael@0: }
michael@0: assertEq(log, '5;4;3;2;1;0;');
michael@0: assertEq(map.size, 6);