JavaScript prototype实现静态方法(原型继承)

• 原型继承 

function Circle (radius) {
  // instance members
  this.radius = radius
}

// Prototype members
Circle.prototype.draw = function() {
  console.log('draw')
}

const c1 = new Circle(1)
const c2 = new Circle(2)

• 修改原型方法

function Circle (radius) {
  // instance members
  this.radius = radius
}

// Prototype members
Circle.prototype.draw = function() {
  console.log('draw')
}
Circle.prototype.toString = function() {
  console.log(`radius is ${this.radius}`)
}
const c1 = new Circle(1)
const c2 = new Circle(2)

•  原型方法调用实例方法

function Circle (radius) {
  // instance members
  this.radius = radius
  this.move = function() {
    console.log('move')
  }
}

// Prototype members
Circle.prototype.draw = function() {
  this.move()
  console.log('draw')
}
Circle.prototype.toString = function() {
  console.log(`radius is ${this.radius}`)
}
const c1 = new Circle(1)
const c2 = new Circle(2)

• 实例方法调用原型方法 

function Circle (radius) {
  // instance members
  this.radius = radius
  this.move = function() {
    this.draw()
    console.log('move')
  }
}

// Prototype members
Circle.prototype.draw = function() {
  console.log('draw')
}
Circle.prototype.toString = function() {
  console.log(`radius is ${this.radius}`)
}
const c1 = new Circle(1)
const c2 = new Circle(2)

• 枚举原型方法和实例方法

function Circle (radius) {
  // instance members
  this.radius = radius
  this.move = function() {
    console.log('move')
  }
}

// Prototype members
Circle.prototype.draw = function() {
  console.log('draw')
}
Circle.prototype.toString = function() {
  console.log(`radius is ${this.radius}`)
}
const c1 = new Circle(1)
// instance members
console.log(Object.keys(c1))
// All members
for (const key in c1) {
  console.log(key)
}
// Prototype members
for (const key in c1) {
  if (c1.hasOwnProperty(key)) {
    console.log(key)
  }
}