instanceof XMLHttpRequest test On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". PASS (new Audio()) instanceof Audio is true PASS (new Array()) instanceof Audio is false PASS (new Image()) instanceof Image is true PASS (new Array()) instanceof Image is false PASS (new Option()) instanceof Option is true PASS (new Array()) instanceof Option is false PASS (new WebKitCSSMatrix()) instanceof WebKitCSSMatrix is true PASS (new Array()) instanceof WebKitCSSMatrix is false PASS (new WebKitPoint()) instanceof WebKitPoint is true PASS (new Array()) instanceof WebKitPoint is false PASS (new Worker('instanceof-operator-dummy-worker.js')) instanceof Worker is true PASS (new Array()) instanceof Worker is false PASS (new XMLHttpRequest()) instanceof XMLHttpRequest is true PASS (new Array()) instanceof XMLHttpRequest is false PASS (new XSLTProcessor()) instanceof XSLTProcessor is true PASS (new Array()) instanceof XSLTProcessor is false PASS successfullyParsed is true TEST COMPLETE