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// Map.prototype.delete works whether the key is present or not.
var m = new Map;
var key = {};
// when the map is new
assertEq(m.delete(key), false);
assertEq(m.has(key), false);
// when the key is present
assertEq(m.set(key, 'x'), m);
assertEq(m.delete(key), true);
assertEq(m.has(key), false);
assertEq(m.get(key), undefined);
// when the key has already been deleted
assertEq(m.delete(key), false);
assertEq(m.has(key), false);