Encapsulating collections in JavaScript 🎁

0-before.js

class Team {
  constructor(members) {
    this._members = members;
  }
 
  get members() {
    return this._members;
  }

  set members(members) {
    this._members = members;
  }
}

const team = new Team([ mike, john] );

// Add a member
team.members.push(peter);

// Remove a member
const index = team.members.indexOf(peter);
team.members.splice(index, 1);

// Replace the members
team.members = [ mike, john, peter ];

// Get the number of members
console.log(team.members.length);

// Iterate through the members
for (let member of team.members) {
  console.log(member.fullname);
}

1-after.js

class Team {
  constructor(members) {
    // We store a "copy" of the collection
    this._members = members.slice();
  }
 
  addMember(member) {
    return this._members.push(peter);
  }

  removeMember(member) {
    const index = this._members.indexOf(member);
    return this._members.splice(index, 1);
  }

  set members(members) {
    this._members = members.slice();
  }
  
  get length() {
    return this._members.length;
  }

  [Symbol.iterator]() {
    return this._people[Symbol.iterator]();
  }
}

// Add a member
team.addMember(peter);

// Remove a member
team.removeMember(peter);

// Replace the members
team.members = [ mike, john, peter ];

// Get the number of members
console.log(team.length);

// Iterate through the members
for (let member of team) {
  console.log(member.fullname);
}