1.typeof
console.log(typeof "");
console.log(typeof 1);
console.log(typeof true);
console.log(typeof null);
console.log(typeof undefined);
console.log(typeof []);
console.log(typeof function(){});
console.log(typeof {});
2.instanceof
1 console.log("1" instanceof String);
2 console.log(1 instanceof Number);
3 console.log(true instanceof Boolean);
4 // console.log(null instanceof Null);
5 // console.log(undefined instanceof Undefined);
6 console.log([] instanceof Array);
7 console.log(function(){} instanceof Function);
8 console.log({} instanceof Object);
3.constructor
4.Object.prototype.toString.call()
