var o1 = {a:1,b:1};
var o2 = {b:2};
var o3 = Object.assign(o1,o2);
console.log(JSON.stringify(o3));
//字符串对象
var s_obj= new String("123");
console.log(typeof(s_obj)); //object
console.log(s_obj instanceof String); //true
var s = "123";
console.log(typeof(s)); //string