function type(data){
var a;
if(data == null || data === a) return (data===a?a:data)+'';
return {}.toString.call(data).slice(8,-1).toLowerCase();
}
console.log(type(window));
console.log(type(123));
console.log(type(new Number()));
console.log(type(alert));
console.log(type([]));
console.log(type());
console.log(type(true));