在类中的函数之前,"get"关键字是什么？

Question

get这个ES6课程意味着什么？我该如何参考这个功能？我该怎么用？

class Polygon {
  constructor(height, width) {
    this.height = height;
    this.width = width;
  }

  get area() {
    return this.calcArea()
  }

  calcArea() {
    return this.height * this.width;
  }
}

Answer 1

It means the function is a getter for a property.

To use it, just use it's name as you would any other property:

'use strict'
class Polygon {
  constructor(height, width) {
    this.height = height;
    this.width = width;
  }

  get area() {
    return this.calcArea()
  }

  calcArea() {
    return this.height * this.width;
  }
}

var p = new Polygon(10, 20);

alert(p.area);

Answer 2

摘要:

所述get关键字将对象属性到功能结合.现在查找此属性时,将调用getter函数.然后,getter函数的返回值确定返回哪个属性.

例:

const person = {
    firstName: 'Willem',
    lastName: 'Veen',
    get fullName() {
        return `${this.firstName} ${this.lastName}`;
    }

}

console.log(person.fullName);
// When the fullname property gets looked up
// the getter function gets executed and its
// returned value will be the value of fullname

Answer 3

It is getter, same as Objects and Classes in OO JavaScript. From the MDN Docs for get:

The get syntax binds an object property to a function that will be called when that property is looked up.

Answer 4

或更简单的方法，它只需键入函数名即可调用函数而无需用户“()”

以上两个函数同等关注person.fullName()和person.fullName

const person = {
    firstName: 'Willem',
    lastName: 'Veen',
    fullName() {
        return `${this.firstName} ${this.lastName}`;
    }

}

console.log(person.fullName());

const person = {
    firstName: 'Willem',
    lastName: 'Veen',
    get fullName() {
        return `${this.firstName} ${this.lastName}`;
    }

}

console.log(person.fullName);