CustomEvent is already polyfilled by ie9.js

[brettz9]

Can just utilize standard in own function since already polyfilled

[brettz9]

This is awesome, thanks!

Btw, the reason I added undef to:

(function (undef) {
// Check against "undef" without needing to do a "typeof x === 'undefined'" check
}());

...is because otherwise, browsers not following ES 5 will allow this:

undefined = 5; // This had been allowed!
alert(typeof undefined === 'undefined'); // false!

I could have also done the following:

(function (undefined) {
// Check against "undefined"; it is safe now
}());