🟡ES6类

class关键字声明类,new关键字创建新的类实例

contructor

contructor(x, y, ...)生成类实例时该方法就会执行

class Info {
  constructor (name) {
    console.log(`New Info Class: ${name} Created`)
  }
}

const info = new Info('Info');
// > New Info Class: Info Created

contructor()默认返回this将实例暴露出来,若返回一个非原始类型时外部就得不到对象实例

class Info {
  constructor (name) {
    console.log(`New Info Class: ${name} Created`)
    return {}
  }
}

const info = new Info('Info');

console.log([info, info instanceof Info]);

/**
 * New Info Class: Info Created
 * [ {}, false ]
 */

添加方法/属性

class Person {
  constructor (name, age) {
    this.name = name
    this.age = age
  }

  about () {
    console.log(`${this.name} is ${this.age} years old`)
  }
}

const me = new Person('Jonathan', 20)

me.about()
console.log([me.name, me.age])
/**
 * Jonathan is 20 years old
 * ['Jonathan', 20]
 */

属性拦截器

class使用get,set关键字定义属性拦截器

class Student {
  static gradeType = ['A', 'B', 'C', 'D', 'F']

  constructor (name, age, gradeCode) {
    this.name = name
    this.age = age
    this.grade = gradeCode
  }

  get grade () {
    return this.gradeName
  }

  set grade (value) {
    this.gradeName = this.gradeType[value]
  }
}

const student = new Student('Jonathan', 20, 1)

console.log(student.grade)

静态属性

私有方法/属性

继承

《Class 的基本语法 (阮一峰)》