[ES6] Extends class in ES6 vs ES5 subclass

ES6 class with extends and super:

class Tree {
  constructor(size = '10', leaves = {spring: 'green', summer: 'green', fall: 'orange', winter: null}) {
    this.size = size;
    this.leaves = leaves;
    this.leafColor = null;
  }

  changeSeason(season) {
    this.leafColor = this.leaves[season];
    if (season === 'spring') {
      this.size += 1;
    }
  }
}

class Maple extends Tree {
  constructor(syrupQty = 15, size, leaves) {
    super(size, leaves);
    this.syrupQty = syrupQty;
  }

  changeSeason(season) {
    super.changeSeason(season);
    if (season === 'spring') {
      this.syrupQty += 1;
    }
  }

  gatherSyrup() {
    this.syrupQty -= 3;
  }
}

const myMaple = new Maple(15, 5);
myMaple.changeSeason('fall');
myMaple.gatherSyrup();
myMaple.changeSeason('spring');

 

How this is written in ES5:

function Tree() {
  this.size = size || 10;
  this.leaves = leaves || {spring: 'green', summer: 'green', fall: 'orange', winter: null};
  this.leafColor;
}

Tree.prototype.changeSeason = function(season) {
  this.leafColor = this.leaves[season];
  if (season === 'spring') {
    this.size += 1;
  }
}

function Maple (syrupQty, size, leaves) {
  Tree.call(this, size, leaves);
  this.syrupQty = syrupQty || 15;
}

Maple.prototype = Object.create(Tree.prototype);
Maple.prototype.constructor = Maple;

Maple.prototype.changeSeason = function(season) {
  Tree.prototype.changeSeason.call(this, season);
  if (season === 'spring') {
    this.syrupQty += 1;
  }
}

Maple.prototype.gatherSyrup = function() {
  this.syrupQty -= 3;
}

const myMaple = new Maple(15, 5);
myMaple.changeSeason('fall');
myMaple.gatherSyrup();
myMaple.changeSeason('spring');

We use 'Tree.call(this)' to pass context, 'this' is refer to Maple because of Clourse.

Then we create a new object by using Object.create()

Maple.prototype = Object.create(Tree.prototype);