Demo of secret diary encapsulation example

secretDiary.js

// using classes together
// lower cohesion

class SecretDiary {
  constructor() {
    this.entries = []
    this.isLocked = true
  }

  lock() {
    this.isLocked = true
  }

  unlock() {
    this.isLocked = false
  }

  addEntry(str) {
    if (this.isLocked) { throw new Error }

    this.entries.push(str)
  }

  getEntries() {
    if (this.isLocked) { throw new Error }

    return this.entries
  }
}

// Higher cohesion - Example 1
class Diary {
  constructor() {
    this.entries = []
  }

  addEntry(str) {
    this.entries.push(str)
  }

  getEntries() {
    return this.entries
  }
}

class SecretDiary {
  constructor() {
    this.diary = new Diary()
    this.isLocked = true
  }

  lock() {
    this.isLocked = true
  }

  unlock() {
    this.isLocked = false
  }

  addEntry(str) {
    if (this.isLocked) { throw new Error }

    this.diary.addEntry(str)
  }

  getEntries() {
    if (this.isLocked) { throw new Error }

    return this.diary.getEntries()
  }
}

// Higher cohesion - Example 2
class Lock {
  constructor() {
    this.isLocked = false
  }

  lock() {
    this.isLocked = true
  }

  unlock() {
    this.isLocked = false
  }
}

class SecretDiary {
  constructor() {
    this.entries = []
    this.lock = new Lock()
  }

  lock() {
    this.lock.lock()
  }

  unlock() {
    this.lock.unlock()
  }

  addEntry(str) {
    if (this.lock.isLocked) { throw new Error }

    this.entries.push(str)
  }

  getEntries() {
    if (this.lock.isLocked) { throw new Error }

    return this.entries
  }
}