zoukankan      html  css  js  c++  java
  • JavaScript_4_数据类型

    1. JavaScript对大小写敏感。

    2. JavaScript是脚本语言。浏览器会在读取代码时,逐行地执行脚本代码。而对于传统编程来说,会在执行前对所有代码进行编译。

    3. 变量什么用var, 是弱类型。

       JavaScript数据类型:数字、字符串、布尔、数组、对象、null、undefined

       JavaScript变量均为对象。当你声明一个变量时,就创建了一个新的对象。

    <!DOCTYPE html>
    <html>
    <head>
        <title></title>
        <meta charset="utf-8" />
    </head>
    <body>
    
        <script>
            document.write("Hello 
                                        World" + "</br>");
            var x;// undefined
            var n = null;//null
            var y = 6;//数字
            var f = 3.1415;//浮点数
            var s = "Hello World";//字符串
            var carname = '大众';//也可以单引号
            var answer1 = "He is called 'yoyo'"; 
            var answer2 = 'He is called"yoyo"';
            var b = true;//bool型
    
            //JavaScript变量均为对象,当您声明一个变量时,就创建了一个新的对象
            var z1 = new Number;
            var z2 = new String;
            var z3 = new Boolean;
            var z4 = new Array;
            var z5 = new Object;
    
            //数组
            var cars1 = new Array();
            cars1[0] = "Audi";
            cars1[1] = "BMW";
            cars1[2] = "Volvo";
            var cars2 = new Array("Audi", "BMW", "Volvo");
            var cars3 = ["Audi", "BMW", "Volvo"];
    
            //对象:对象由花括号分隔。在括号内部,对象的属性以名称和值对的形式来定义
            var person = {
                firstname: "yoyo",
                lastname: "xiao",
                id: 506
            };
    
    
            document.write(x + "</br>");
            document.write(n+ "</br>");
            document.write(y + "</br>");
            document.write(f + "</br>");
            document.write(s + "</br>");
            document.write(carname + "</br>");
            document.write(answer1 + "</br>");
            document.write(answer2 + "</br>");
            document.write(b + "</br>");
            document.write(z1 + "</br>");
            document.write(z2 + "</br>");
            document.write(z3 + "</br>");
            document.write(z4 + "</br>");
            document.write(z5 + "</br>");
    
            for (i = 0; i < cars3.length;i++)
            {
                document.write(cars3[i] + "</br>");
            }
            document.write(person.firstname + "</br>");
            document.write(person["lastname"] + "</br>");
        </script>
    
    </body>
    </html>
  • 相关阅读:
    flume 使用遇到问题及解决
    定时任务 Linux cron job 初步使用
    java instrumentation &JVMTI
    Java远程执行Shell命令
    No input clusters found in output/ZS_TEST_OUTPUT3404268420/clusters-0/part-randomSeed. Check your -c argument.
    asp.net core 中读取post 方式来的内容
    C#程序 权限不够的解决方案
    wamp下安装https 实现 ssl 协议,主要是编写小程序通讯
    如何让thinkpad X1C 用U盘 安装上专业版win10
    php 5.4 5.5 如何连接 ms sqlserver
  • 原文地址:https://www.cnblogs.com/xiao9426926/p/6599657.html
Copyright © 2011-2022 走看看