Throw my own exception in javascript?

I can catch builtin exceptions using JS, but can I throw my own? I can’t seem to find the right way to do it.

var someVar = false;

function Start() {
	try {
		if (someVar) {throw "Error1";}
		else {throw "Error2";}
	}
	catch(err) {
		if (err.Message == "Error1") {print ("Oh no!");}
		else {print ("Argh!");}
	}
}

–Eric

Super. You’re the best.