收藏
PHPz批改状态：合格
老师批语：
<!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>javascript数据类型和分支循环</title></head><body><script>// javascript数据类型分为// 1、原始类型： Number String Boolean undefined null// 2、引用类型：array object function// numberconsole.log("这是number:" + 123);//stringconsole.log("这是string:" + "123");//booleanconsole.log("这是boolean:" + false);//undefinedlet a;console.log("这是undefined:" + a);//nulllet b = null;console.log("这是null:" + b);//arraylet arr = ["小明", "男", "16", "16cm"];console.log("这是array:" + arr);let obj1 = [{ name: "手机", num: 2, price: 5000 },{ name: "电脑", num: 5, price: 6000 },{ name: "相机", num: 4, price: 2000 },];console.log("这是array:" + obj1[0].name);//objectlet obj = {name: "Tom",age: 18,height: "180cm",fun: function () {console.log("这是一个function.");},};console.log("这是一个object:" + obj["age"]);console.log("这是一个object:" + obj.age);obj.fun();//查看数据类型用typeofconsole.log(typeof function () {});console.log(arr instanceof Object);//回调函数function f1() {}function f2(f1) {console.log("这是回调函数" + typeof f1);}f2(f1);//这是闭包函数function f3() {return function () {return "hello world";};}console.log("这是闭包函数" + f3()());</script><script>//分支和循环// 1、单分支if (true) {console.log("这是一个单分支");}//2、双分支if (false) {console.log("这个是双分支,真的");} else {console.log("这个是双分支,假的");}//3、三元运算let res;isNaN(123) ? (res = "是") : (res = "不是");console.log("这" + res + "三元运算");//多分支let age = 20;if (age < 18) {console.log("年龄小于18岁");} else if (age >= 18 && age < 25) {console.log("正是青春年华");} else if (age >= 25) {console.log("差不多了");}//switch判断分支//必须要用true做为switch入口判断条件switch (true) {case age < 18:console.log("年龄小于18岁");breack;case age >= 18 && age < 25: {console.log("正是青春年华");break;}default: {console.log("差不多了");}}//for循环，for of 循环 ，for in 循环arr = [9, 4, 2, 7, 4];obj = {product: "电视",num: 3,price: 300,fun: function () {},};//for循环for (let i = 0; i < arr.length; i++) {console.log("for循环:" + arr[i]);}//for of 循环for (let item of arr) {console.log("for of循环:" + item);}for (let item of arr.values()) {console.log("for of循环值:" + item);}for (let item of arr.keys()) {console.log("for of循环键:" + item);}//for in 循环for (let key in obj) {console.log("for in循环键:" + key);}//这里只能发obj[key]访问，不能用obj.key .obj[key],key不能有引号for (let key in obj) {console.log("for in循环值:" + obj[key]);}</script></body></html>
Copyright 2014-2025 https://www.php.cn/ All Rights Reserved | php.cn | 湘ICP备2023035733号
