How to choose Reflect.ownKeys () and Object.keys ()

This article mainly explains "how to choose Reflect.ownKeys () and Object.keys ()". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "how to choose Reflect.ownKeys () and Object.keys ()".

Consider a question: how to traverse the Keys of Object in JavaScript and encounter the two methods of Reflect.ownKeys (obj) and Object.keys (obj), what is the difference between them?

Let's first look at an example:

Const obj = {a: 5, b: 5}; console.log (Reflect.ownKeys (obj)); console.log (Object.keys (obj)); / / Result / / ['asides,' b'] / / ['asides,' b']

It doesn't seem to be any different. Go through the documents of the two methods and learn:

Object.keys (obj) returns an array of enumerable properties of a given object in the same order that property names are returned when traversing the object in a normal loop.

The result returned by Reflect.ownKeys (obj) is equivalent to:

Object.getOwnPropertyNames (target) .concat (Object.getOwnPropertySymbols (target))

The Object.getOwnPropertyNames () method returns an array of property names of all its own properties of the specified object, including properties that cannot be enumerated but do not include symbol values as names.

The Object.getOwnPropertySymbols () method returns an array of all the Symbol properties of a given object itself.

Reflect.ownKeys (obj) equals to returning all the properties of a given object as an array.

Let's see the difference through the following code:

Var testObject = {[Symbol ('1')]: 1, a: 2}; Object.defineProperty (testObject, 'myMethod', {value: function () {alert ("Non enumerable property");}, enumerable: false}); console.log (Object.keys (testObject)); / / [' a'] console.log (Reflect.ownKeys (testObject); / / ['asides,' myMethod', Symbol (1)]

Summary

Object.keys (obj): the result is all enumerable key on object

Reflect.ownKeys (obj): the result is all key.

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