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js实例演示变量
P粉314265155
Original
337 people have browsed it

js基础

  1. <!DOCTYPE html>
  2. <html lang="zh-CN">
  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>js演示</title>
  8. </head>
  9. <body>
  11.     <script>  
  13.     // 声明变量 a,且初始化赋值
  14.     let a =10;
  15.     let b =20;
  16.     console.log( a);
  17.     console.log(b);
  18.     // 匿名函数
  19.     {
  20.     a + b ;
  21.       let c =1;
  22.       c =  a + b ;
  23.       console.log(c);
  24.       console.log(typeof(a + b ));
  25.       let d = '朱老师' ;
  26.       console.log( d);
  27.       console.log( typeof (d));
  29.       console.log(typeof(d +c));
  30.     }
  31.     // console.log(c);    块的  作用域原因不能访问
  32.     // {
  33.     //     // 在js中, 字符串的拼装: "+",二边至少有一个字符串
  34.     //     let s = 'Hello ' + 'World';
  35.     //     console.log(s);
  36.     //     console.log('a=', a, ', b=', b);
  37.     //     console.log(a + b);
  38.     //     console.log(a + '10');
  39.     //     console.log(typeof (a + '10'));
  40.     //   }
  42. // 命名函数
  43.    function sum ( a,b  ){
  44.    return  a  +  b ;
  45.    }
  46.      console.log(sum(10 , ',朱老师' ));
  47.    console.log(sum(1, 2 ));
  51.    function sum (j  , k ) {
  52.    let e = j+ k ;
  53.     return e ;
  54.    }
  55.  console.log(sum (11, 20));
  59. // 全局作用域
  61. let email = '123@qq.com';
  62. {
  63.     console.log(email);
  64. }
  66. let email2 = '456@qq.com' ;
  67.    {
  68.     let email2 = ' 789@qq.com';
  69.     console.log(email2);
  70. }
  71. console.log(email2);
  73. // 我是常量
  74. const H = 66  ;
  75. console.log(H);
  77. //变量 命名法
  78. // 1、驼峰    大驼峰  UserName   小驼峰  userName   动词+名词
  79. // 2、蛇形     user_name
  81. //常量 命名法
  82. // USERNAME
  85. // 命名函数
  86.  function getName(userName){
  87.   return  'hello,' +userName ;
  88.  }
  89.  console.log( getName('朱老师'));
  92. //  匿名函数
  93. let getName1 = function (userName1){
  94.  return 'hello' + userName1 ;
  96. }
  97.  console.log(getName1('灭绝老师'));
  98.       // let getUserName = function (username) {
  99.       //   return 'Hello, ' + username;
  100.       // };
  101.       // console.log(getUserName('马老师'));
  102.       // console.log(getUserName('牛老师'));
  103.       // console.log(getUserName('羊老师'));
  105.   //     console.log(lhusername)(
  106.   // function (lhusername) {
  107.   //   return 'hello,' + lhusername ;
  108.   // }
  110.   //     );
  112. // 阅读及焚
  113.       console.log(
  114.         (function (qjusername) {
  115.           return 'Hello, ' + qjusername;
  116.         })('灭绝老师')
  117.       )  ;
  119. // 简化匿名函数
  120. // 去掉 function  及形参的括弧，在形参的右侧增加 =>  胖箭头  
  121. getName1 = userName1 =>  {
  122.  return 'hello,' + userName1 ;
  123. }
  124.  console.log(getName1('go老师'));
  126. // 再次简化 ，去掉{   }   ，去掉return 注意又有分号
  128. getName1 = userName1 =>  
  129. 'hello,' + userName1 ;
  130.  console.log(getName1('猫老师'));
  133. let f = x  => x * 2  ;
  134. console.log(f (3));
  136. f =(x ,z) => 5*7 ;
  137. console.log(f());
  138. f =(x ,z) => x+ z ;
  139. console.log(f(4,9));
  142. f =() => 'hello ,桌面花纹'
  143. console.log(f());
  144.     </script>
  145. </body>
  146. </html>

Correcting teacher：PHPzPHPz

Correction status：qualified

Teacher's comments：
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