JS 04 Date_Math_String_Object

Date

<script>
//1.Date對象
        var d1 = new Date();
//Thu May 02 2019 14:27:19 GMT+0800 (中國標準時間)
         console.log(d1);
//轉成2019/5/2 下午2:27:19
        console.log(d1.toLocaleString());
 //距離1900年經過年數
        console.log(d1.getYear());//119
//獲取當前紀年
        console.log(d1.getFullYear());//2019
//獲取一年中當前月份
        console.log(d1.getMonth()); //4,   0-11
        
        
//獲取一個月中的日期
        console.log(d1.getDate());

//時
        console.log(d1.getHours());
//分
        console.log(d1.getMinutes());
//秒
        console.log(d1.getSeconds());
    
//設置月份時，記得值為0-11
        var d2 = new Date(2012,11,12,12,12,12);
        console.log(d2.toLocaleString());//2012/12/12 下午12:12:12
        
 //可以創建一個距離1970年經過的毫秒數
        var d3 = new Date(1528980372222);
        console.log(d3.toLocaleString())
</script>

Math

<script >
    console.log(Math.random()) // [0,1) 隨機數
    console.log(Math.abs(-5))  //求取絕對值

    console.log(Math.round(4.5)); //四捨五入

    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次冪

    console.log(Math.PI); //圓周率
</script>

String

<script type="application/javascript">
        //var str = new String("aabbcc");
        var str2 = "aabdcbc";
        //console.log(str);
        console.log(str2);

        //轉化大小寫
        console.log(str2.toUpperCase()); //大寫
        console.log(str2.toLowerCase()); //小寫
        //返回指定索引處的字母
        console.log(str2.charAt(3));

        //返回指定字母首次出現的索引
        console.log(str2.indexOf("b"));
        //返回指定字母最後一次出現的索引
        console.log(str2.lastIndexOf("b"));

        //截取子字元串，從x位置截取y個字元
        console.log(str2.substr(2,3));
        //截取子字元串，從x位置截到y位置
        console.log(str2.substring(2,3));

        //字元串length屬性表示字元的個數
        console.log(str2.length)

    </script>

Object

<script type="application/javascript">
        //1.在js中，我們可以使用Object對象來表述一個人
        var obj = new Object();
        //2.在js中，對象有個特點：屬性可以動態的添加
        //添加屬性
        obj.name = "laowang";
        //修改屬性的值
        obj.name = "laoma";
        //刪除屬性
        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);


        //封裝的人“類”
        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("喬峰",25);
        console.log(p2.name);
        console.log(p2.age);
        p2.skill = "降龍十八掌";
        console.log(p1.skill);
        console.log(p2.skill);

        //為所有對象都添加屬性
        Person.prototype.money = 8888;
        Person.prototype.like = ["吃飯","睡覺","打豆豆"];
        Person.prototype.eat = function(){
            alert("吃飯了，好開心！");
        }

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

        p1.like.push("寫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>