'use strict';
if (true) {
var animal = "cat"
let fruit = "apple"
}
//animal可以输出，但是fruit不可以输出，因为变量定义为let，是块级作用域
console.log(animal);
console.log(fruit);
'use strict';
const animal = "cat";
console.log(animal);
//错误：这里重复声明了
const animal = 'dong';
console.log(animal);
// const 限制的是赋值的动作
const fruit = [];
fruit.push("apple");
fruit.push("lemon");
//这样是可以的
console.log(fruit);
//这里会报错因为fruit是常量
fruit =[];
console.log(fruit);
'use strict';
function animals() {
return ["cat", "dog", "mouse"]
}
var tmp = animals(), cat = tmp[0], dog = tmp[1], mouse = tmp[2];
console.log(cat, dog, mouse);
//结构数组
let [animal1, animal2, animal3] = animals();
console.log(animal1, animal2, animal3);
'use strict';
function login() {
return {username: 'rc', userpassword: '123456'}
}
//解构对象，前面的是对象的key
let {username: name, userpassword: passowrd} = login();
console.log(name, passowrd);
'use strict';
let day = '星期一';
let str = `今天是${day}`;
console.log(str);
'use strict';
let username = "rc", password = "123";
let loginInfo = login `用户名是${username} 密码是${password}`;
function login(string, ...values) {
// ["用户名是", " 密码是", "", raw: Array(3)]
// 0: "用户名是"
// 1: " 密码是"
// 2: ""
console.log(string);
//["rc", "123"]
console.log(values);
}
console.log(loginInfo);
'use strict';
let username = "rc", password = "123";
let loginInfo = `用户名是${username} 密码是${password}`;
//判断字符串以什么开头 ,这里返回true
console.log(loginInfo.startsWith("用户名"));
//判断字符串以什么结尾 ,这里返回true
console.log(loginInfo.endsWith(password));
//判断字符串包含什么字符，这里返回false
console.log(loginInfo.includes("1234"));
'use strict';
function login(username = 'rc', password = '123') {
return `用户名是${username} 密码是${password}`
}
//不传入函数值，就会使用默认的值
console.log(login());
'use strict';
let username = ['张三', '李四'];
//输出 ['张三', '李四']
console.log(username);
//输出张三 李四(这里将数组的每一个元素输出)
console.log(...username);
// 输出["王五", "张三", "李四"]
let otheruser =['王五',...username];
console.log(otheruser);
'use strict';
//...在参数里面代表剩余操作符
function username(firstUser, secondUser, ...otherUser) {
//console中的otherUser表示将...otherUser放大otherUser数组中
console.log(firstUser, secondUser, otherUser);
// console.log(firstUser, secondUser, ...otherUser); 这里表示的就是展开操作符
}
// 输出 aaa bbbb ["cccc", "ddddd"]
username("aaa", 'bbbb', 'cccc', 'ddddd');
'use strict';
function meeting(when, where, {person, activity} = {}) {
console.log(when, where, person, activity);
}
//输出：12点 广州 rc movie
meeting('12点', '广州', {person: 'rc', activity: 'movie'});
'use strict';
let login = function () {
};
//输出login
console.log(login.name);
let logout = function MyLogout() {
};
//输出MyLogout
console.log(logout.name);
'use strict';
// let login = (username, password) => username + password;
//如果有其他操作，可以在外面包裹{}
// let login = (username, password) => {
// return username + password;
// };
// 等价于
// let login = function login(username, password) {
// return username + password;
// };
//输出rc123
console.log(login('rc', '123'));
'use strict';
let myUserName = 'rc', myPassword = '123';
let login = {
username: myUserName,
password: myPassword
};
//输出{username: "rc", password: "123"}
console.log(login);
//如果变量名和属性一样的话可以直接加属性，不用指定值
let myLogin = {
myUserName,
myPassword
};
//输出{myUserName: "rc", myPassword: "123"}
console.log(myLogin);
let otherLogin ={
login:function () {
}
};
//等价于
// let otherLogin ={
// login () {
//
// }
// };
'use strict';
let fruit = {};
fruit.apple ='苹果';
//如果属性名有空格，可以这样[`green apple`]添加属性
fruit[`green apple`] ='青苹果';
let otherApple ='other apple';
//也可以通过定义一个变量来添加属性
fruit[otherApple]='其他苹果';
//输出{apple: "苹果", green apple: "青苹果", other apple: "其他苹果"}
console.log(fruit);
'use strict';
//true
console.log(+0==-0);
//true
console.log(+0===-0);
//false
console.log(NaN == NaN);
//false
console.log(NaN === NaN);
//false
console.log(Object.is(+0,-0));
//true
console.log(Object.is(NaN,NaN));
'use strict';
let userInfo={};
Object.assign(userInfo,{userName:'rc',password:'123'});
//{userName: "rc", password: "123"}
console.log(userInfo);
'use strict';
let username = {
getUserName() {
return 'rc';
}
};
let password = {
getPassword() {
return '123';
}
};
let userInfo =Object.create(username);
//rc
console.log(userInfo.getUserName());
//true
console.log(Object.getPrototypeOf(userInfo)===username);
'use strict';
let username = {
getUserName() {
return 'rc';
}
};
let password = {
getPassword() {
return '123';
}
};
let userInfo = {
__proto__: username
};
//rc
console.log(userInfo.getUserName());
//true
console.log(Object.getPrototypeOf(userInfo) === username);
userInfo.__proto__ = password;
//123
console.log(userInfo.getPassword());
//true
console.log(Object.getPrototypeOf(userInfo) === password);
'use strict';
let username = {
getUserName() {
return 'rc';
}
};
let user ={
__proto__:username,
getUserName(){
return super.getUserName()+"123";
}
};
//rc123
console.log(user.getUserName());
'use strict';
function chef(foods) {
let i = 0;
return {
next() {
let done = (i >= foods.length);
let value = !done ? foods[i++] : undefined;
return {
value: value,
done: done,
}
}
}
}
let rc = chef(['🍎', '🍊']);
//{value: "🍎", done: false}
console.log(rc.next());
//{value: "🍊", done: false}
console.log(rc.next());
//{value: undefined, done: true}
console.log(rc.next());
'use strict';
function* chef(foods) {
// yield '🍎';
// yield '🍊';
for (let i = 0; i < foods.length; i++) {
yield foods[i];
}
}
let rc = chef(['🍎','🍊']);
//{value: "🍎", done: false}
console.log(rc.next());
//{value: "🍊", done: false}
console.log(rc.next());
//{value: undefined, done: true}
console.log(rc.next());
'use strict';
class User {
constructor(userName) {
this.userName = userName;
}
getUserName() {
console.log(this.userName);
}
}
let userInfo = new User("rc");
//rc
userInfo.getUserName();
'use strict';
class User {
constructor() {
this.userName = [];
}
get user() {
return this.userName;
}
set user(userName) {
this.userName.push(userName);
}
}
let userInfo = new User();
userInfo.user="张三";
userInfo.user="李四";
//["张三", "李四"]
console.log(userInfo.user);
'use strict';
class User {
static printUser(user){
console.log(user);
}
}
//静态方法不需要实例化类
//rc
User.printUser('rc');
'use strict';
class Person {
constructor(name, age) {
this.name=name;
this.age=age;
}
info(){
return `${this.name},${this.age}`
}
}
class Rc extends Person{
constructor(name,age){
super(name,age)
}
}
//Rc {name: "rc", age: "18"}
console.log(new Rc("rc","18"));
'use strict';
let userNames = new Set(['张三', '李四', '王五', '张三']);
//Set(3) {"张三", "李四", "王五"}
console.log(userNames);
userNames.add('rc');
//Set(4) {"张三", "李四", "王五", "rc"}
console.log(userNames);
//true
console.log(userNames.has('rc'));
//true
console.log(userNames.delete('rc'));
//张三
//李四
// 王五
userNames.forEach(user => {
console.log(user)
});
userNames.clear();
//Set(0) {}
console.log(userNames);
'use strict';
let food = new Map();
let fruit = {}, cook = function () {
}, dessert = '甜点';
food.set(fruit, '苹果');
food.set(cook, '🍴');
food.set(dessert, '甜点');
console.log(food);
console.log(food.size);
console.log(food.get(fruit));
food.delete(dessert);
console.log(food.has(dessert));
food.forEach(((value, key) => {
console.log(`${key}==${value} `)
}));
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