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>

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