when do you use Object.defineProperty()

Question

I\'m wondering when I should use

Object.defineProperty

to create new properties for an object. I\'m aware that I\'m able to set things lik

Answer 1

Summary:

In Javascript Objects are collections of key-value pairs. Object.defineProperty() is a function which can define a new property on an object and can set the following attributes of a property:

• value : The value associated with the key
• writable : if writable is set to true The property can be updated by assigning a new value to it. If set to false you can't change the value.
• enumerable : if enumerable is set to true Property can be accessed via a for..in loop. Furthermore are the only the enumerable property keys returned with Object.keys()
• configurable : If configurable is set to false you cannot change change the property attributes (value/writable/enumerable/configurable), also since you cannot change the value you cannot delete it using the delete operator.

Example:

let obj = {};


Object.defineProperty(obj, 'prop1', {
      value: 1,
      writable: false,
      enumerable: false,
      configurable: false
});   // create a new property (key=prop1, value=1)


Object.defineProperty(obj, 'prop2', {
      value: 2,
      writable: true,
      enumerable: true,
      configurable: true
});  // create a new property (key=prop2, value=2)


console.log(obj.prop1, obj.prop2); // both props exists

for(const props in obj) {
  console.log(props);
  // only logs prop2 because writable is true in prop2 and false in prop1
}


obj.prop1 = 100;
obj.prop2 = 100;
console.log(obj.prop1, obj.prop2);
// only prop2 is changed because prop2 is writable, prop1 is not


delete obj.prop1;
delete obj.prop2;

console.log(obj.prop1, obj.prop2);
// only prop2 is deleted because prop2 is configurable and prop1 is not