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JS学习之变量、函数、数组、对象、作用域及闭包
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JS学习之变量、函数、数组、对象、作用域及闭包

变量有数值（number）、字符串（string）、布尔值（boolean）、undefined 、 null
引用类型有：数组array、对象object、函数function三种

  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>初识js</title>
  8.   </head>
  9.   <body></body>
  10.   <script>
  11.     //   变量
  12.     let myName = "zhangDeng";
  13.     console.log(myName);
  14.     // alert
  15.     //alert(myName);
  16.     let price = 99;
  17.     console.log(price);
  18.     // 变量有数值（number）、字符串（string）、布尔值（boolean）、undefined 、 null
  19.     // 引用类型有：数组array、对象object、函数function三种
  20.     // 数组
  21.     const price1 = [33, 44, 55, 66];
  22.     console.log(price1[0], price1[1]);
  23.     // 对象
  24.     const shop = {
  25.       name: "京东便利店",
  26.       room: 150,
  27.       price: 8899,
  28.     };
  29.     console.log(shop.name, shop.price, shop.room);
  30.     const shop1 = {
  31.       "my name": "京东便利店",
  32.       "my-room": 150,
  33.     };
  34.     console.log(shop1["my name"]);
  35.     // 实际开发过程中数组和对象结合使用
  36.     const shop2 = [
  37.       { name: "饼干", num: 2, price: 3.5 },
  38.       { name: "面包", num: 4, price: 4.5 },
  39.       { name: "水果", num: 6, price: 7 },
  40.     ];
  41.     console.log(shop2);
  42.     // 函数
  43.     function getTotal(name) {
  44.       return "hello" + name;
  45.     }
  46.     console.log(getTotal("张老师"));
  47.     // typeof是返回判断变量类型;
  48.     console.log(typeof getTotal);
  49.     console.log(getTotal.name);
  50.     console.log(getTotal.length);
  51.     // 数组里包含函数
  52.     const arr = [
  53.       123,
  54.       "bbb",
  55.       [1, 2, 3, 4],
  56.       { a: 1, b: 2, c: 3 },
  57.       function age() {
  58.         console.log("my age is 33");
  59.       },
  60.     ];
  61.     console.log(arr[0]);
  62.     console.log(arr[4]());
  63.     // 封装函数 对于重复使用的代码，可以考虑封装，实现复用
  64.     function sum(num1, num2) {
  65.       let total = 0;
  66.       total = num1 + num2;
  67.       console.log("total=", total);
  68.     }
  69.     sum(2, 3);
  70.     // 胖箭头
  71.     // 1.如果执行语句只有一条，可以不写大括号；
  72.     // 2.如果参数只有一个，可以不写参数外部的括号；
  73.     // 3。如果没有参数，括号必须写
  74.     add = () => 11 + 3;
  75.     console.log(add());
  76.     // 全局变量，函数可以从外向内传递，无法由内向外传递
  77.     // 闭包练习  满足两个条件： 父子函数及自由变量
  78.     //父函数
  79.     function p(n) {
  80.       // 子函数
  81.       function m() {
  82.         return n++;
  83.       }
  84.       //   返回子函数
  85.       return m;
  86.     }
  87.     // 声明父函数
  88.     const r = p(10);
  89.     // 返回
  90.     r();
  91.     console.log(r());
  92.     console.log(r());
  93.     console.log(r());
  94.     console.log(r());
  96.     // 经典闭包IIFE;
  97.     let jishu = (function (i) {
  98.       return function () {
  99.         return i++;
  100.       };
  101.     })(99);
  102.     console.log(jishu());
  103.     console.log(jishu());
  104.     console.log(jishu());
  105.     console.log(jishu());
  106.     console.log(jishu());
  107.   </script>
  108. </html>
Correcting teacher：天蓬老师天蓬老师

Correction status：qualified

Teacher's comments：
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