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ES6

e 1 year ago
parent
ebb29cc3eb
commit
d227482b98
4 changed files with 132 additions and 0 deletions
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  1. 52 0
      JS高级/1.let变量.html
  2. 29 0
      JS高级/2.const变量.html
  3. 34 0
      JS高级/3.let const var 区别.html
  4. 17 0
      JS高级/ES6.html

+ 52 - 0
JS高级/1.let变量.html
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+<!DOCTYPE html>
 
+<html lang="en">
 
+<head>
 
+    <meta charset="UTF-8">
 
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
 
+    <title>Document</title>
 
+</head>
 
+<body>
 
+    <script>
 
+        // 变量声明 赋值 
+        var a = 1;
 
+        let b = 2;
 
+        console.log(b);
 
+        /**
 
+         * var 与 let 区别
 
+         * 1.var 具备变量提升，let不具备变量提升
 
+         * 2.let 不能重复声明
 
+         * 3.临时失效区 在同一区域内 不能使用let进行同命名
 
+        */
 
+        // 变量提升    
+       console.log(a1);
 
+        //console.log(b1);
 
+       var a1;
 
+       let b1 = 0;
 
+       var a = 6;
 
+       console.log(a);
 
+       let b2 = 12;
 
+       function fn() {
 
+        // var c = 3;
 
+       }
 
+       fn();
 
+    //    console.log(c);
 
+
 
+    var a2 = '2222';
 
+       function fn2() {
 
+        var a2 = '111';
 
+        console.log(a2); // 111
 
+       }
 
+       fn2();
 
+       console.log(a2); // 2222
 
+
 
+       let a3 = '2222';
 
+       function fn2() {
 
+        let a3 = '111';
 
+        // let a3 = '2222'
 
+        console.log(a3);
 
+       }
 
+       fn2();
 
+       console.log(a3);
 
+    </script>
 
+</body>
 
+</html>

+ 29 - 0
JS高级/2.const变量.html
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+<!DOCTYPE html>
 
+<html lang="en">
 
+<head>
 
+    <meta charset="UTF-8">
 
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
 
+    <title>Document</title>
 
+</head>
 
+<body>
 
+    <script>
 
+        /**
 
+         * const 特点
 
+         * 1.去用于声明常量;
 
+         * 2.变量名是大写的;
 
+         * 3.不能重复声明；
 
+         * 4.赋值不可重复修改
 
+         * 5.不能变量提升
 
+        */
 
+       var a;
 
+       const  PI = 3.14;
 
+       const E = 2;
 
+    //    const PI = 3.1415926;
 
+       const Vase = 12;
 
+       Vase = 14;
 
+       console.log(Vase)
 
+       console.log(A2);
 
+       const A2 = '12';
 
+    </script>
 
+</body>
 
+</html>

+ 34 - 0
JS高级/3.let const var 区别.html
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+<!DOCTYPE html>
 
+<html lang="en">
 
+<head>
 
+    <meta charset="UTF-8">
 
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
 
+    <title>Document</title>
 
+</head>
 
+<body>
 
+    <script>
 
+        /**
 
+         * let const 和var 的区别
 
+         * 1.作用域的区别：let const 具有块级作用域；var可以作用与全局 不能跨函数访问
 
+         * 2.var可以变量提升，let const不可以
 
+         * 3.var具有全局属性:window
 
+         * 4.var可以重复声明，let const不可以重复声明
 
+        */
 
+        //变量提升:变量在声明前使用，就是变量提升
 
+       if(true) {
 
+        var a = 0;
 
+        let b = 0;
 
+        const C = 0;
 
+       }
 
+       console.log(a);
 
+        // console.log(b);
 
+        // console.log(C);
 
+       function fn() {
 
+        var a1 = '我的名字';
 
+       }
 
+       fn();
 
+       console.log(a1);
 
+
 
+    </script>
 
+</body>
 
+</html>

+ 17 - 0
JS高级/ES6.html
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+<!DOCTYPE html>
 
+<html lang="en">
 
+<head>
 
+    <meta charset="UTF-8">
 
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
 
+    <title>Document</title>
 
+</head>
 
+<body>
 
+    
+    <!-- 
+        js由三部分组成：
 
+        ECMAScript(es6,es5,es3,es7,es8...)
 
+        BOM
 
+        DOM
 
+     -->
 
+</body>
 
+</html>