笔记：2.26课程记录

2025-02-26 09:31:39 +08:00
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+<!-- vue-1-3.html -->
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>Document</title>
+  </head>
+  <body>
+    <script>
+      if (true) {
+        let myName = "储久良"; // let的作用域是代码块级
+        var myAge = 57; // 在代码块中使用var定义的变量可以在代码块之外使用
+        const PI = 3.14159; // const的作用域是代码块级
+        console.log("PI=", PI); // 3.14159
+      }
+      console.log("年龄:" + myAge); // 57
+      // console.log("PI="+PI);          //  报错
+      // console.log(myName + "欢迎您!"); //报错
+      // const定义变量指向的那个内存地址不得改动。
+      const numberArr = [1, 2, 3, 4, 5, 6, 7]; // 赋值
+      numberArr.push(10, 20, 30); // 可以执行
+      console.log(numberArr); // 输出所有元素
+      // numberArr = [15, 2, 3, 4, 5, 6, 7]; // 报错，不能重新赋值
+      console.log(numberArr);
+      // //let不存在变量提升
+      // console.log(a);  //报错
+      // let a = "apple";
+
+      console.log(b);  //undefined，是一个值
+      var b = "banana";
+
+      //
+      // console.log(x);
+      // console.log(y);
+      // var 与function 预解析的区别
+      console.log(number);//这里可以以后定义先调用，提升
+      var number = 2022;
+      console.log(number);
+      func(1000, 2000);//函数允许后定义先调用
+      function func(n1, n2) {
+        var total = n1 + n2;
+        console.log(total);
+      }
+
+      let [x, y, ...z] = ["z","a","b","c"];//..是运算符，意思为后续直到Z
+      console.log(x);
+      console.log(y);
+      console.log(z);
+      // var sum = (num1, num2) => {        //箭头函数，与其对应
+      //   return num1 + num2;
+      // };
+      var sum = (num1,num2) =>num1+num2
+      // var sum = function (num1, num2) { 
+      //   return num1 + num2;
+      // };
+      console.log(sum(100, 200));
+      var f = (id, name) => ({ id: id, name: name });//返回对象的时候要用小括号括起来
+      console.log("f", f(10, "AAAA"));
+
+      //拷贝对象（深拷贝）
+      let p1 = { name: "qiyue", age: 23 };
+      let obj = { ...p1 };
+      console.log(obj); //{name: "qiyue", age: 23}之后修改也无联系
+      obj.name="ddd"
+      console.log(obj)
+      console.log(p1)
+      //拷贝对象（浅拷贝）之后修改同步更新，依旧有联系，引用更新，相当于别名，一个东西 
+      let pp = p1
+      pp.name = "ddd"
+      console.log(pp)
+      console.log(p1)
+
+      //合并对象
+      let age1 = { age: 24 };
+      let name1 = { name: "qiyue" };
+      let p2 = {};
+      p2 = { ...age1, ...name1 };
+      console.log(p2); //{age: 24, name: "qiyue"}
+      //如果p2中原本有name,age属性会被覆盖
+
+      let string1 = `Hey,
+       	can you stop angry now?`;//模板字符串1.可换行2.可在字符串里面加入变量
+      console.log(string1);
+      function fun() {
+        return "Chu Jiu Liang!";
+      }
+      let string2 = `Welcom to ${fun()}`;
+      console.log(string2); // Welcom to  Chu Jiu Liang!
+    </script>
+  </body>
+</html>