JS: Reflect .getOwnPropertyDescriptor

Reflect.getOwnPropertyDescriptor

Reflect.getOwnPropertyDescriptor(obj, key)

• Return the Property Attributes in the form of Property Descriptor.
• If the property doesn't exist, returns undefined.
• If obj is not an object, throw TypeError.

const jj = { dog: 4 };
const xout = Reflect.getOwnPropertyDescriptor(jj, "dog");
console.log(xout);
// { value: 4, writable: true, enumerable: true, configurable: true }

Example. check if a property is enumerable

// check if a property is enumerable
console.assert(
 Reflect.getOwnPropertyDescriptor({ dog: 4 }, "dog").enumerable,
);

Example. non-exist key

// non-exist key
console.assert(
 Reflect.getOwnPropertyDescriptor({ dog: 4 }, "yyyyy") === undefined,
);

Object .getOwnPropertyDescriptor vs Reflect .getOwnPropertyDescriptor

• JS: Object .getOwnPropertyDescriptor 👎
• JS: Reflect .getOwnPropertyDescriptor

Object .getOwnPropertyDescriptor is older. It has a problem when the argument is a primitive type. It implicitly convert it to a object.

Reflect .getOwnPropertyDescriptor is new. Also, it is a replacement for Object.prototype.propertyIsEnumerable because that won't work if object has the same property name.