class类与extends,super等的用法与字符串,数组常用API

1.class类与extends,super等的用法

1.1 class类

=>1.构造函数并声明->属性->2.方法->3.静态成员

let User = class {
  constructor(uname, email) {
    this.uname = uname
    this.email = email
  }
    say() {
    return `${this.uname}: ( ${this.email} )`
  }
    static nation = '中国'
}
const user = new User('Mr.Y', 'mmmyyy@qq.com')
console.log(user.say())
console.log(User.nation)
运行结果：
Mr.Y: ( mmmyyy@qq.com )
中国

1.2 extends,super的用法

class Child extends User {
  constructor(uname, email, gender) {
    super(uname, email)
    this.gender = gender
  }
  say() {
    return `${super.say()}, (${this.gender})`
  }
}
const child = new Child('黄氏', 'hs@qq.com', '男')
console.log(child.say())
运行结果：
黄氏: ( hs@qq.com ), (男)

2.字符串,数组常用API

2.1.length 属性

let xName = 'My name is Yasinjan'
console.log('length = ', xName.length)
运行结果:
length =  19

2.2 charAt(), 索引 -> 成员

let xName = 'My name is Yasinjan'
console.log(xName[4])
运行结果:
a

2.3 indexOf(): 成员 -> 索引

let xName = 'My name is Yasinjan'
console.log(xName.indexOf('Y'))
运行结果:
11

2.4 replace()替换

let xName = 'My name is Yasinjan'
console.log(xName.replace('Yasinjan', 'GongLi'))
运行结果:
My name is GongLi

2.5 split: 字符串 -> 数组

let xName = 'My name is Yasinjan'
console.log(xName.split('', 5))
运行结果:
[ 'M', 'y', ' ', 'n', 'a' ]