JS: Reflect.getOwnPropertyDescriptor

(new in ECMAScript 2015)

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 object, throw a TypeError exception.

🟢 tip: This is a improved version of Object.getOwnPropertyDescriptor because it fixed the problem of auto convert arg. It's also a replacement for Object.prototype.propertyIsEnumerable because that won't work if object has the same property name.

const jj = { pp: 4 };

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

console.assert(Object.keys(xout).length === 4);
console.assert(xout.value === 4);
console.assert(xout.writable);
console.assert(xout.enumerable);
console.assert(xout.configurable);

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

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