Tests basic correctness of ES WeakMap object On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". PASS WeakMap instanceof WeakMap is false PASS WeakMap.prototype instanceof WeakMap is false PASS new WeakMap() instanceof WeakMap is true PASS WeakMap() threw exception TypeError: calling WeakMap constructor without new is invalid. PASS map.set(0, 1) threw exception TypeError: Attempted to set a non-object key in a WeakMap. PASS map.set(0.5, 1) threw exception TypeError: Attempted to set a non-object key in a WeakMap. PASS map.set('foo', 1) threw exception TypeError: Attempted to set a non-object key in a WeakMap. PASS map.set(true, 1) threw exception TypeError: Attempted to set a non-object key in a WeakMap. PASS map.set(false, 1) threw exception TypeError: Attempted to set a non-object key in a WeakMap. PASS map.set(null, 1) threw exception TypeError: Attempted to set a non-object key in a WeakMap. PASS map.set(undefined, 1) threw exception TypeError: Attempted to set a non-object key in a WeakMap. PASS map.get(0) is undefined. PASS map.get(0.5) is undefined. PASS map.get('foo') is undefined. PASS map.get(true) is undefined. PASS map.get(false) is undefined. PASS map.get(null) is undefined. PASS map.get(undefined) is undefined. PASS map.has(0) is false PASS map.has(0.5) is false PASS map.has('foo') is false PASS map.has(true) is false PASS map.has(false) is false PASS map.has(null) is false PASS map.has(undefined) is false PASS map.delete(0) is false PASS map.delete(0.5) is false PASS map.delete('foo') is false PASS map.delete(true) is false PASS map.delete(false) is false PASS map.delete(null) is false PASS map.delete(undefined) is false PASS map.set(new String('foo'), 'foo') is map PASS map.get(new String('foo')) is undefined. PASS map.has(new String('foo')) is false PASS map.set(object, 'foo') is map PASS map.has(object) is true PASS map.get(object) is 'foo' PASS map.delete(object) is true PASS map.has(object) is false PASS map.delete(object) is false PASS map.get(object) is undefined. PASS successfullyParsed is true TEST COMPLETE