JS 04 Date_Math_String_Object

Date

<script>
//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());//
//获取当前纪年
        console.log(d1.getFullYear());//
//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())
</script>

Math

<script >
    console.log(Math.random()) // [0,1) 随机数
    console.log(Math.abs(-5))  //求取绝对值

    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
</script>

String

<script type="application/javascript">
        //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"));
        //返回指定字母最后一次出现的索引
        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)

    </script>

Object

<script type="application/javascript">
        //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)

    </script>