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javascript (常量、变量、函数)使用
秋闲独醉
Original
287 people have browsed it
  1. <!DOCTYPE html>
  2. <html lang="en">
  3.   <head>
  4.     <meta charset="UTF-8" />
  5.     <meta http-equiv="X-UA-Compatible" content="IE=edge" />
  6.     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  7.     <title>javascript基础</title>
  8.   </head>
  9.   <body>
  10.     <!-- javascript代码可以被包含在<script></script>标签内，也可以包含在.js结尾的文件中 -->
  11.     <!-- 第一种 -->
  12.     <script>
  13.       // js代码
  14.     </script>
  15.     <!-- 第二种 -->
  16.     <!-- <script src="javascript.js"></script> -->
  17.     <!-- javascript 变量的声名和定义 -->
  18.     <script>
  19.       // 变量名命名：必须只能有字母、数字、下划线、$,四种组合在一起；
  20.       // 必须只能是字母、$、下划线开头。
  21.       // 一般用小写字母。
  22.       let a = "123";
  23.       let a_ = "123";
  24.       let _a = "123";
  25.       let $_a = "123";
  26.       let $_a1 = "123";
  27.       //   以var 定义 的变量是全局变量，以let 定义的变里视作用域决定，可全局可局部
  28.       {
  29.         var b = "88";
  30.       }
  31.       {
  32.         let c = "77";
  33.       }
  34.       console.log(b);
  35.       //   console.log(c);  //这个报错，因为c是局部变量，不能在全局使用。
  37.       //   + 符号的使用，可以用作两个字符串之间的连接
  38.       console.log("我是" + "一个好人");
  39.       //常量的声名和赋值，都用同时，这个于变量不一样。
  40.       //常量名通常是大写字母加下划线
  41.       APP_NAME = "这是一个APP";
  42.       console.log(APP_NAME);
  43.       APP_NAME = "这不是一个APP";
  44.       console.log(APP_NAME);
  45.       //函数名通常用小驼峰命名
  46.       let name = "佚名";
  47.       function setUserName(param) {
  48.         name = param;
  49.       }
  50.       setUserName("小丸子");
  51.       console.log(name);
  52.       //匿名函数
  53.       let getUserName = function (username) {
  54.         return "HELLO " + username;
  55.       };
  56.       console.log(getUserName("小不点"));
  57.       let getUserName2 = (username) => {
  58.         return "hello" + username;
  59.       };
  60.       console.log(getUserName2("小物件"));
  61.     </script>
  62.   </body>
  63. </html>
Correcting teacher：PHPzPHPz

Correction status：qualified

Teacher's comments：
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