Q267: How do you prevent an object from being extend - JavaScript Internals (521 Qs)

The Object.preventExtensions() method is used to prevent new properties from ever being added to an object. In other words, it prevents future extensions to the object. Let's see the usage of this property,

javascript

  const newObject = {};
  Object.preventExtensions(newObject); // NOT extendable

  try {
    Object.defineProperty(newObject, "newProperty", {
      // Adding new property
      value: 100,
    });
  } catch (e) {
    console.log(e); // TypeError: Cannot define property newProperty, object is not extensible
  }