Tests for ES6 arrow function prototype property On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". () => {} PASS typeof af1.prototype is 'undefined' PASS af1.hasOwnProperty('prototype') is false (a) => {a + 1} PASS typeof af2.prototype is 'undefined' PASS af2.hasOwnProperty('prototype') is false (x) => x + 1 PASS typeof af3.prototype is 'undefined' PASS af3.hasOwnProperty('prototype') is false af1.prototype = function (x) { return x + 1;} PASS typeof af1.prototype is 'function' PASS af1.prototype.toString() is 'function (x) { return x + 1;}' PASS af1.hasOwnProperty('prototype') is true delete af1.prototype PASS typeof af1.prototype is 'undefined' PASS af1.hasOwnProperty('prototype') is false PASS successfullyParsed is true TEST COMPLETE