Object.defineProperty()

ES5+

Defines a new property directly on an object, or modifies an existing property.

Syntax

Object.defineProperty(obj, prop, descriptor)

obj Object

The object on which to define the property

prop string

The name of the property to define

descriptor Object

The descriptor for the property being defined

Object

The object that was passed to the function

JavaScript

const obj = {};
Object.defineProperty(obj, 'x', {
  value: 42,
  writable: false
});
console.log(obj.x);
obj.x = 100;
console.log(obj.x);

Output:

// 42 42