基本包装类型

//引用类型和基本包装类型的主要区别就是对象的生存期
var s1 = "some text";
s1.color = "red";
var s2 = s1.substring(2);
console.log(s1.color); //undefined  相当于自动执行了s1=null;

var s3 = new String("some text");//基本包装类型
s3.color = "red";
console.log(s3.color);//red

//Boolean 类型
//Number 类型
//String 类型
var str = "hello world";
str.color = "red";
str = str.concat("!")  //连接符，如果不赋给 str 则原来str的值不变
console.log(str.length);  //11
console.log(str.charAt(2)); //l
console.log(str.charCodeAt(2));//108

console.log(str[3]);//l
console.log(str.color);//undefined
console.log(str.slice(2));//llo world!
console.log(str.substring(4));//o world!
console.log(str.slice(3,7));//lo w
console.log(str.substring(4,7));//o w
console.log(str.indexOf("o"));//4
console.log(str.lastIndexOf("o"));//7
console.log(str.indexOf("o",6));//7
console.log(str.lastIndexOf("o",5));//4
console.log(str.toLocaleUpperCase());  //"HELLO WORLD"
console.log(str.toUpperCase());        //"HELLO WORLD"
console.log(str.toLocaleLowerCase());  //"hello world"
console.log(str.toLowerCase());        //"hello world"
//字符串的模式匹配
var text = "cat,bat,sat,fat";
var pattern = /.at/
var matches = text.match(pattern);//返回第一个匹配项
console.log(matches); //["cat", index: 0, input: "cat,bat,sat,fat"]

var pos = text.search(/at/);//返回第一个匹配项的索引，若果有返回1，没有返回-1
console.log(pos);//-1

var repl =text.replace('at','ba');
console.log(repl); //cba,bat,sat,fat

var replg =text.replace(/at/g,'ba');
console.log(replg); //cba,bba,sba,fba

console.log(String.fromCharCode(104,101));//he  //String 构造函数的静态方法