Lesson 88 – JavaScript Reflect API

The Reflect API was introduced in ES6 to provide methods for interceptable JavaScript operations. It works hand-in-hand with Proxy, and provides a standardized way to perform object operations that were previously done in less elegant ways.

Why Reflect?

• To make operations like get, set, delete, etc., more declarative and functional.
• To improve code consistency and avoid direct manipulation of object internals.
• To provide default behavior for traps in Proxy objects.

Core Reflect Methods

Here are some of the most commonly used methods:

const person = {
  name: "John",
  age: 30,
};

// get a property
console.log(Reflect.get(person, "name")); // John

// set a property
Reflect.set(person, "age", 31);
console.log(person.age); // 31

// check if a property exists
console.log(Reflect.has(person, "name")); // true

// delete a property
Reflect.deleteProperty(person, "age");
console.log(person); // { name: 'John' }

Using Reflect with Proxy

When writing proxy handlers, it's recommended to use Reflect methods to maintain default behavior:

const user = {
  username: "coder123",
};

const handler = {
  get(target, prop) {
    console.log(`Getting property: ${prop}`);
    return Reflect.get(target, prop); // default behavior
  },
};

const proxy = new Proxy(user, handler);

console.log(proxy.username); // logs "Getting property: username" then "coder123"

More Useful Reflect Methods

Try Your Hand

const book = {
  title: "JavaScript Mastery",
  pages: 400,
};

Reflect.set(book, "author", "Jane Doe");
console.log(book);

const hasPages = Reflect.has(book, "pages");
console.log("Has pages:", hasPages);

Reflect.deleteProperty(book, "pages");
console.log(book);

Summary

• The Reflect API provides a functional way to perform object operations.
• It works well with Proxy to provide default behaviors.
• Reflect methods improve readability and consistency in code.