JavaScript Basics: Reflect

Reflect is a global object in ES6 and later that provides the reflection API for JavaScript. Most strongly typed languages, such as Java, provide a reflection API which you can use to inspect and fine-tune the low-level structure of objects. Since JavaScript is a dynamic language, most of that functionality is already present in the language. However, Reflect provides a more meaningful place for these functionalities.

Reflect is not a function, so it is not callable (and it cannot be used with the new operator). It is just a global object and all its methods are static methods.

The methods of Reflect are the same methods that are available for ES6 proxies. However, proxies are not the subject of discussion in this post.

Here is a list of methods available from Reflect global object:

    defineProperty
    getOwnPropertyDescriptor
    getPrototypeOf
    setPrototypeOf
    preventExtensions
    isExtensible
    construct
    apply
    deleteProperty
    has
    ownKeys
    get
    set

Some of these methods are similar to the methods available on Object and have similar functions, albeit sometimes a little different. For example, Reflect.defineProperty has the same functionality as Object.defineProperty, except that it returns a boolean indicating whether or not the operation was successful, whereas Object.defineProperty returns the first argument as its return value.

Reflect.getOwnPropertyDescriptor works in the same way as Object.getOwnPropertyDescriptor.

Similarly, Reflect.getPrototypeOf works in the same way as Object.getPrototypeOf. However, for setPrototypeOf, the return value is different. Object.setPrototypeOf returns the given object, while Reflect.setPrototypeOf returns a boolean value indicating whether or not the operation was successful.

Reflect.preventExtensions works like Object.preventExtensions, except that if the given argument is not an object, it throws a TypeError. In the case of Object, the argument is coerced to an object. The same situation exists with isExtensible.

The rest of the methods will be discussed in future posts.

JavaScript Basics: Reflect

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