JavaScript—引用类型

引用类型和基本包装类型的区别：
程序1

var s2=Object();
s2.color="red";
console.log(s2.color);

程序2

var s1="some text";
s1.color="red";
console.log( typeof s1);
console.log(s1.color);

程序3

var s1=new String("some text");
s1.color="red";
console.log( typeof s1);
console.log(s1.color);

程序4

var s1=new Object("some text");
s1.color="red";
console.log(s1 instanceof String );
console.log(s1 instanceof Object );

程序5

var person={
    "first name":"bruce",
    "age":19
}
console.log(person["first name"]);

程序6

var num=10;
console.log(num.toString(2));
console.log(num.toFixed(2));

程序7

var str="你好 world";
console.log(str.length);