[Javascript] Proxy - Snippets

Blog: https://dev.to/marclipovsky/discovering-the-power-of-javascript-proxy-after-all-this-time-4627

 

Lazy loading:

const lazyLoadHandler = {
  get: function (target, property) {
    if (!target[property]) {
      target[property] = expensiveComputation();
    }
    return target[property];
  },
};

const lazyLoadedObject = new Proxy({}, lazyLoadHandler);
const result = lazyLoadedObject.expensiveProperty; // Calls expensiveComputation() on first access

 

Readonly:

const readOnlyHandler = {
  set: function (target, property, value) {
    if (property === 'readOnly') {
      throw new Error('Cannot modify read-only property');
    }
    target[property] = value;
    return true;
  },
};

const protectedObject = new Proxy({ readOnly: true }, readOnlyHandler);
protectedObject.newProperty = 'some value'; // OK
protectedObject.readOnly = false; // Throws Error