//1.Date对象 var d1 = new Date(); //Thu May 02 2019 14:27:19 GMT+0800 (中国标准时间)  console.log(d1); //转成2019/5/2 下午2:27:19  console.log(d1.toLocaleString()); //距离1900年经过年数 console.log(d1.getYear());//119 //获取当前纪年 console.log(d1.getFullYear());//2019 //获取一年中当前月份 console.log(d1.getMonth()); //4,   0-11 //获取一个月中的日期  console.log(d1.getDate()); //时  console.log(d1.getHours()); //分  console.log(d1.getMinutes()); //秒  console.log(d1.getSeconds()); //设置月份时，记得值为0-11 var d2 = new Date(2012,11,12,12,12,12);
        console.log(d2.toLocaleString());//2012/12/12 下午12:12:12 //可以创建一个距离1970年经过的毫秒数 var d3 = new Date(1528980372222);
        console.log(d3.toLocaleString()) 

 console.log(Math.random()) // [0,1) 随机数 console.log(Math.abs(-5)) //求取值  console.log(Math.round(4.5)); //四舍五入  console.log(Math.ceil(3.1)); //天花板  console.log(Math.floor(3.9)); //地板  console.log(Math.pow(2,20)); //x的y次幂  console.log(Math.PI); //圆周率 

 //var str = new String("aabbcc"); var str2 = "aabdcbc"; //console.log(str);  console.log(str2); //转化大小写 console.log(str2.toUpperCase()); //大写 console.log(str2.toLowerCase()); //小写 //返回指定索引处的字母 console.log(str2.charAt(3)); //返回指定字母首次出现的索引 console.log(str2.indexOf("b")); //返回指定字母一次出现的索引 console.log(str2.lastIndexOf("b")); //截取子字符串，从x位置截取y个字符 console.log(str2.substr(2,3)); //截取子字符串，从x位置截到y位置 console.log(str2.substring(2,3)); //字符串length属性表示字符的个数  console.log(str2.length) 

 //1.在js中，我们可以使用Object对象来表述一个人 var obj = new Object(); //2.在js中，对象有个特点：属性可以动态的添加 //添加属性 obj.name = "laowang"; //修改属性的值 obj.name = "laoma"; //删除属性 delete obj.name; function factory(name,age){ var obj = new Object();
            obj.name = name;
            obj.age = age; return obj;
        } var per1 = factory("laowang",30);
        console.log(per1.name); var c1 = factory("benz",3);
        console.log(c1.name); //封装的人“类” function Person(name,age){ this.name = name; this.age = age;
        } var p1 = new Person("zhangsan",20);
        console.log(p1.name);
        console.log(p1.age); var p2 = new Person("乔峰",25);
        console.log(p2.name);
        console.log(p2.age);
        p2.skill = "降龙十八掌";
        console.log(p1.skill);
        console.log(p2.skill); //为所有对象都添加属性 Person.prototype.money = 8888;
        Person.prototype.like = ["吃饭","睡觉","打豆豆"];
        Person.prototype.eat = function(){
            alert("吃饭了，好开心！");
        }

        console.log(p1.money);
        console.log(p2.money);

        p1.like.push("写Java");

        console.log(p1.like);
        console.log(p2.like);

        p1.money = 88888;

        console.log(p1.money);
        console.log(p2.money); function Student(){ this.sno = Math.random();
        }
        Student.prototype = new Person("lisi",8); var s1 = new Student();
        console.log(s1.name);
        console.log(s1.age);
        console.log(s1.sno);
        console.log(s1.money);
        console.log(s1.like)