EcmaScript | ES6 proxy.js

const target = {}
// Create proxy with no interceptors
const proxy = new Proxy(target, {})

proxy.test = 5

console.log(target.test) // Expected output: 5
console.log(proxy.test) // Expected output: 5

const arr = [1, 2, 3]
// Create proxy with interceptors
const handler = {
    get(target, prop) {
      // This interceptor will return default value if no value found
      const defaultValue = 0
      return target[prop] || defaultValue
    },
    set(target, prop, value) {
      // This interceptor prevent adding no number values
      if (typeof value === 'number') {
        target[prop] = value
        return true
      }
      return false
    }
}

const proxyWithInterceptors = new Proxy(arr, handler)
console.log(proxyWithInterceptors[0]) // Expected output: 1
console.log(proxyWithInterceptors[1]) // Expected output: 2
console.log(proxyWithInterceptors[2]) // Expected output: 3
console.log(proxyWithInterceptors[3]) // Expected output: 0 (default value)

proxyWithInterceptors.push(4)
console.log(proxyWithInterceptors[3]) // Expected output: 4
proxyWithInterceptors.push('Hello World') // Error since string is pushed to the arr