javascript中的3种继承实现方法

//Shape - superclassfunction Shape() { this.x = 0; this.y = 0;}Shape.prototype.move = function(x, y) {  this.x += x;  this.y += y;  console.info("Shape moved.");};// Rectangle - subclassfunction Rectangle() { Shape.call(this); //call super constructor.}Rectangle.prototype = Object.create(Shape.prototype);var rect = new Rectangle();rect instanceof Rectangle //true.rect instanceof Shape //true.rect.move(1, 1); //Outputs, "Shape moved."

const util = require('util');const EventEmitter = require('events');function MyStream() {  EventEmitter.call(this);}util.inherits(MyStream, EventEmitter);MyStream.prototype.write = function(data) {  this.emit('data', data);}var stream = new MyStream();console.log(stream instanceof EventEmitter); // trueconsole.log(MyStream.super_ === EventEmitter); // truestream.on('data', (data) => { console.log(`Received data: "${data}"`);})stream.write('It works!'); // Received data: "It works!"

exports.inherits = function(ctor, superCtor) { if (ctor === undefined || ctor === null)  throw new TypeError('The constructor to "inherits" must not be ' +            'null or undefined'); if (superCtor === undefined || superCtor === null)  throw new TypeError('The super constructor to "inherits" must not ' +            'be null or undefined'); if (superCtor.prototype === undefined)  throw new TypeError('The super constructor to "inherits" must ' +            'have a prototype'); ctor.super_ = superCtor; Object.setPrototypeOf(ctor.prototype, superCtor.prototype);};

Object.setPrototypeOf = Object.setPrototypeOf || function (obj, proto) { obj.__proto__ = proto; return obj; }

class Polygon { constructor(height, width) {  this.name = 'Polygon';  this.height = height;  this.width = width; }}class Square extends Polygon { constructor(length) {  super(length, length);  this.name = 'Square'; }}