GUIDE: OOP Inheritance In Javascript

Level: Advanced

Prerequisites: Primitive Types VS Reference Types, First Class Functions And Higher Order Functions, OOP In Javascript

❯❯ Implementing Inheritance Using Constructor Function

If we want to use inheritance in a constructor function we need to utilize the .call() method from the Function.prototype object.

Implementing inheritance using .call()

/* Create the constructor function from which to inherit */
const BankAccount = function (balance) {
  this.balance = balance;
};

/* Create an inheriting constructor function */
const SavingsAccount = function (balance, initDeposit, percent) {
  /* use constructor of BankAccount with this pointing to savingsAccount */
  BankAccount.call(this, balance);
  this.initDeposit = initDeposit;
  this.percent = percent;
};
/* Create prototype linkage (using prototypal chaining)  */
SavingsAccount.prototype = Object.create(BankAccount.prototype);

❯❯ Implementing Inheritance Using Classes

If we use the class syntax we need to use the 'extends' keyword and the super() constructor inside the inheriting class constructor.

implement inheritance with class syntax

class BankAccount = {
  constructor(balance) {
    this.balance = balance;
  }
};

class SavingsAccount extends BankAccount = {
  constructor(balance, initDeposit, percent) {
    super(balance);
    this.initDeposit = initDeposit;
    this.percent = percent;
  }
};

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