Privates in JavaScript Symbol, medium, using Symbol, es6

private-using-symbol-es6.js

const _addBalance = Symbol('addBalance')
const _logBankChange = Symbol('logBankChange')
const _privateData = Symbol('privateData')

export default class Bank {
  constructor() {
    // public variables
    this.name = 'B7'

    // private variables
    this[_privateData] = {
      balance: 0,
      logs: []
    }
  }
  
  // public methods
  getBalance() {
    return this[_privateData].balance
  }

  addToBalance(count) {
    this[_addBalance](count)
    return this.getBalance()
  }

  // private methods
  [_addBalance](count) {
    this[_logBankChange]('add', count)
    this[_privateData].balance += count
  }

  [_logBankChange](type, count) {
    this[_privateData].logs.push({ type, count })
  }
}