# es2015

**Repository Path**: kangpanwork/es2015

## Basic Information

- **Project Name**: es2015
- **Description**: 重学 JavaScript 之你不一定知道的 ES6
- **Primary Language**: Unknown
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2023-01-02
- **Last Updated**: 2023-01-10

## Categories & Tags

**Categories**: Uncategorized

**Tags**: ES6

## README

# es2015

#### 介绍
重学 JavaScript 之你不一定知道的 ES6

#### 准备工作

1.  vscode 
2.  node
3.  nodemon 开发环境 [https://www.npmjs.com/package/nodemon](https://www.npmjs.com/package/nodemon)
4.  vscode 使用 code 命令新建 js 文件

### Proxy

```js
const person = {
  name: "pankang",
  age: 18,
};

const proxyPerson = new Proxy(person, {
  get(target, property) {
    return property in target ? target[property] : "default";
  },
  set(target, property, value) {
    if (property === "age") {
      if (!Number.isInteger(value)) {
        throw new TypeError(`${value} is not an int`);
      }
    }
    target[property] = value;
  },
});

proxyPerson.age = 19;
console.log(proxyPerson);
```



 

```js
const list = [];
const proxyList = new Proxy(list, {
    set(target, property, value) {
        console.log('set', property, value);
        target[property] = value;
        return target;
    }
});

proxyList.push(100);
```



### Reflect

```js
const obj = {
    name :'zce',
    age: 18
};
console.log('name' in obj);
console.log(delete obj['age']);
console.log(Object.keys(obj));

console.log(Reflect.has(obj, 'name'));
console.log(Reflect.deleteProperty(obj, 'age'));
console.log(Reflect.ownKeys(obj));
```





### Class

```js
class Person {
  constructor(name) {
    this.name = name;
  }
  say() {
    console.log(`hi, my name is ${this.name}`);
  }

  static create(name) {
    return new Person(name);
  }
}
class Student extends Person {
  constructor(name, number) {
    super(name);
    this.number = number;
  }
  hello() {
    super.say();
    console.log(`hi, my number is ${this.number}`)
  }
}
const p = Person.create("tom");
p.say();
const student = new Student('jacky', 100);
student.hello();

```



### Set

```js
const arr = [1, 2, 3, 1, 3, 4, 5];
const result = [...new Set(arr)];
console.log(result);
const rt = Array.from(new Set(arr));
console.log(rt);
```



### Map

```js
const m = new Map();
const tom = { name: "tom" };
m.set(tom, 90);
m.forEach((k,v) => {
    console.log(k, v);
})
```



### Symbol

```js
const name = Symbol();
const person = {
  [name]: "jack",
  say() {
    console.log(this[name]);
  }
};
person.say();
console.log(person[Symbol()]); // undefined
console.log(person[name]);
console.log(Object.keys(person));
console.log(JSON.stringify(person));
console.log(Object.getOwnPropertySymbols(person));
```



### Iterator

```js
const set = new Set(["foo", "bar"]);
for (const item of set) {
  console.log(item);
}
const map = new Map();
map.set("foo", "123");
map.set("bar", "456");
for (const [k, v] of map) {
  console.log(k, v);
}
const iterator = set[Symbol.iterator]();
console.log(iterator.next());

const obj = {
  store: ["foo", "bar", "baz"],
  [Symbol.iterator]: function () {
    let index = 0;
    const self = this;
    return {
      next: function () {
        return {
          value: self.store[index],
          done: index++ >= self.store.length,
        };
      },
    };
  },
};
for (const item of obj) {
  console.log(item);
}

const todos = {
  life: ["吃饭", "睡觉", "打豆豆"],
  learn: ["语文", "数学", "物理"],
  work: ["java", "javaScript", "vue"],

  each: function (callback) {
    const all = [].concat(this.life, this.learn, this.work);
    for (const item of all) {
      callback(item);
    }
  },
};
todos.each(function (item) {
  console.log(item);
});



const todos = {
  life:['吃饭','睡觉','打豆豆'],
  learn:['语文','数学','英语'],
  work:['扫地','端茶','倒水'],
  [Symbol.iterator]:function * () {
    const all = [...this.life, ...this.learn, ...this.work]
    for(const item of all) {
      yield item
    }
  }
}
for (const item of todos) {
  console.log(item);
}


```





### other

```js
const arr = ['foo', 'bar', 'baz', NaN, false, 1];
console.log(arr.indexOf(NaN));
console.log(arr.indexOf('foo'));
console.log(arr.includes(NaN));
console.log(Math.pow(2,10));
console.log(2 ** 10);

const obj = {foo:'foo', bar: 'bar'};
console.log(Object.values(obj));
console.log(Object.entries(obj));
for (const [key,value] of Object.entries(obj)) {
  console.log(key, value);
}

console.log(new Map(Object.entries(obj)));


const p1 = {
  firstname: 'li',
  lastname: 'ming',
  get fullname() {
    return this.firstname + this.lastname;
  }
};
const p2 = Object.assign({}, p1);
p2.firstname = 'liu';
// li ming ?
console.log(p2.fullname);

const des = Object.getOwnPropertyDescriptors(p1);
const p3 = Object.defineProperties({}, des);
p3.firstname = 'liu';
// liu ming
console.log(p3.fullname);



const books = {
  html:5,
  javascript:112,
  css:16,
}

for (const[name, count] of Object.entries(books)) {
  console.log(`${name.padEnd(16,'-')} | ${count.toString().padStart(3,'0')}`)
}
```