Ways to implement Proxy Pattern in Node.js

#node #proxy #pattern

https://grokonez.com/node-js/ways-to-implement-proxy-pattern-in-node-js

Sometimes we may want to access indirectly to an object, via a substitute. That substitute is called Proxy. The Proxy Pattern helps us deal with a proxy object and talk to the actual object. In this tutorial, we're gonna look at 2 ways to implement Proxy Pattern in Node.js:

Using custom Proxy Class
Using Proxy API

Proxy Pattern Overview

The image above shows that Proxy and Subject have the same methods. Proxy forwards each operation to Subject, we can improve Subject's methods with additional pre-processing or post-processing.

Proxy Pattern in Node.js using custom Class

Create Subject class

We create a Bank class with 3 methods:
– deposit() increases cash.
– withdraw() decreases cash.
– total() returns cash.

Bank.js


class Bank {

  constructor() {
    this.cash = 0;
  }

  deposit(amount) {
    this.cash += amount;
    return this.cash;
  }

  withdraw(amount) {
    if (amount <= this.cash) {
      this.cash -= amount;
      return true;
    } else {
      return false;
    }
  }

  total() {
    return this.cash;
  }
}

module.exports = Bank;