Proxy pattern

Proxy Pattern

A proxy is an object that has the same interface as another object and is used in place of that other object. It provides a surrogate or placeholder for another object to control access to it. It intends to add a wrapper and delegation to protect the real component from undue complexity.

It allows us to create placeholder wrappers for objects
A proxy Object allows external access control to the object
Implements the same interface as the original object

Use cases

Caching remotely accessed data
Optimize or pre process data on access
Logging
Encryption
Simulating private and inaccessible properties
Data validation

// External API Service
function CryptocurrencyAPI() {
  this.getValue = function (coin) {
    console.log('Calling External API...')
    switch (coin) {
      case 'Bitcoin':
        return '$8,500'
      case 'Litecoin':
        return '$50'
      case 'Ethereum':
        return '$175'
      default:
        return 'NA'
    }
  }
}

function CryptocurrencyProxy() {
  this.api = new CryptocurrencyAPI()
  this.cache = {}

  this.getValue = function (coin) {
    if (this.cache[coin] == null) {
      this.cache[coin] = this.api.getValue(coin)
    }
    return this.cache[coin]
  }
}

const proxy = new CryptocurrencyProxy()
console.log(proxy.getValue('Bitcoin'))
console.log(proxy.getValue('Litecoin'))

Created 2019-01-23T11:57:03+05:30, updated 2020-08-23T11:04:17+05:30 · History · Edit