Day68 JavaScript、Json

1.思维导图

2.代码部分

ECMAScript：页面结合

  • 内部结合
<head>
    <title>ECMAScript和页面结合之内部结合</title>
    <%--js脚本内部结合--%>
    <script>
        //打印语句
        console.log("js脚本")
    </script>
</head>
<body>
hello javascript
</body>
  • 外部结合
<head>
    <title>ECMAScript和页面结合之外部结合</title>
    <script src="${pageContext.request.contextPath}/myjs.js"></script>
</head>
<body>
</body>
  • typeof方法
        var num = 1;
        console.log(typeof(num));//number
        var str = "abc";
        console.log(typeof(str));//string
        var flag = true;
        console.log(typeof(flag));//boolean
        var obj = null;
        console.log(typeof(obj));//Object
        var num1 ;
        console.log(typeof(num1));//undefined
        var num2 = NaN;
        console.log(typeof num2);//number
  • 流程控制语句：switch
 　　　　　switch (true) {
            case true:
                console.log(true)
                break;
            case false:
                console.log(true)
                break;
        }

        for (var i = 0; i < 10; i++) {
            console.log(i)
        }
  • ECMAScript：全局对象Global
        //parseInt
        var num1 = 1;
        var num2 = "1";
        console.log(num1 + parseInt(num2));
        console.log("--------------------")
        
        //isNaN:判断一个变量是否是NaN
        var num3 = NaN;
        console.log(num3 == NaN);//false
        console.log(num3 === NaN);//false
        console.log(isNaN(num3));//true
        console.log("--------------------")
        
        //eval：计算json字符串，返回js对象
        var jsonStr = '{"username":"root","password":"root"}';
        //不能通过上述的json字符串直接调用username属性和password属性，需要将json字符串转换成js对像
        var jsObject = eval("("+jsonStr+")");
        console.log(jsObject.username + " , " + jsObject.password)   

Java对象转Json字符串

  • Province.java
public class Province {

    private Integer pId;
    private String pName;

    public Province() {
    }

    public Province(Integer pId, String pName) {
        this.pId = pId;
        this.pName = pName;
    }

    public Integer getpId() {
        return pId;
    }

    public void setpId(Integer pId) {
        this.pId = pId;
    }

    public String getpName() {
        return pName;
    }

    public void setpName(String pName) {
        this.pName = pName;
    }

    @Override
    public String toString() {
        return "Province{" +
                "pId=" + pId +
                ", pName='" + pName + '\'' +
                '}';
    }
}
  •  Demo.java
        Province p1 = new Province(1,"卡布奇诺");
        Province p2 = new Province(2,"拿铁");
        //p1 -> json字符串
        String jsonStr1 = "{'pId':1,'pName':'卡布奇诺'}";
        String jsonStr2 = "{'pId':2,'pName':'拿铁'}";//单列集合
        //Province
        List<Province> provinceList = new ArrayList<>();
        provinceList.add(p1);
        provinceList.add(p2);
        // provinceList -> json字符串
        String jsonStr3 = "[{'pId':1,'pName':'卡布奇诺'},{'pId':2,'pName':'拿铁'}]";
        //双列集合
        //entry : 键值对对象
        Map<String,Province> map = new HashMap<>();
        map.put("p1",p1);
        map.put("p2",p2);
        //map -> json字符串
        String jsonStr4 = "[{'p1':{'pId':1,'pName':'卡布奇诺'}},{'p2':{'pId':2,'pName':'拿铁'}}]";

 

posted @ 2020-05-08 21:19  Her4c  阅读(167)  评论(0)    收藏  举报