SOURCE

function MISSING_BREAK(i) {

	switch (i) {
		case 1:;
		case 2:
			console.log('<=2');
			break;
		case 3:
			console.log('>2');
			break;
	}
}


MISSING_BREAK(3);

////////// wrong
function initWrong(obj){
    obj.key = {} || obj.key;
    return obj;
}

var obj = initWrong({});
console.log(obj.key);

obj = initWrong({key:{myname:'user1'}});
console.log(obj.key);

///////// right
function initRight(obj){
    obj.key = obj.key|| {};
    return obj;
}

var obj = initRight({});
console.log(obj.key);

obj = initRight({key:{myname:'user1'}});
console.log(obj.key.myname);