Unlock the Power of Real-Time Data with Server-Sent Events
In today’s fast-paced digital landscape, users expect seamless and up-to-date experiences. Traditional request-response approaches often fall short, especially when dealing with real-time content like live game scores, stock prices, or social media notifications. This is where server-sent events (SSE) come into play, enabling developers to create dynamic applications with a seamless user experience.
What are Server-Sent Events?
Server-sent events are one-directional events sent from the server to the client via HTTP. These events are pushed by the server as soon as they happen, providing users with real-time data. Since users cannot directly influence SSEs, all necessary parameters must be sent on the connection request and processed on the server.
The Limitations of EventSource API
The traditional way to work with SSEs is by using the EventSource API interface, which is included in the HTML5 specification. While it offers a basic connection with the server, receives server messages, and displays errors, it comes with many limitations. For instance, it only allows sending a URL and withCredentials properties, offering limited control over requests and responses.
Introducing Fetch Event Source
Fetch Event Source, developed by Microsoft and contributors, is an open-source package that increases control over real-time data from the server. It allows developers to use all the extended features provided by the Fetch API, including custom request methods, headers, and bodies with specific parameters. This means users can send custom requests, validate responses, and have more control over errors and retry strategies.
Benefits of Fetch Event Source
Fetch Event Source offers several advantages over traditional EventSource API:
- Customizable requests: Send custom request methods, headers, and bodies with specific parameters to the server.
- Response object access: Access the response object from the server, enabling validation and error handling.
- Error control: Have more control over errors and retry strategies, ensuring a seamless user experience.
- Page Visibility API support: Automatically stop server-sent events when the browser window is minimized and resume when it comes back to the viewport, reducing server load.
Building a Real-Time Application with Fetch Event Source
To demonstrate the power of Fetch Event Source, let’s create a practical application that simulates real-time stock price changes in a line graph.
Setting Up the Workspace
Create a new folder for our application, sse-fetch-event-source, and separate workspaces for the frontend and backend.
Implementing the Frontend
Use Create React App to create a fully functional React project. Install Fetch Event Source and recharts library, and set up the frontend code to display the received data in a nice UI.
Implementing the Server-Side
Set up a simple Node.js server using Express and cors package. Create a server that listens for POST requests on the SSE route and generates new data every 5 seconds.
Running the App
Run both the frontend and backend servers separately, and interact between the two by sending requests and receiving server-sent events.
Testing the App
Test the features of Fetch Event Source by opening the developer console, checking the Network tab, and verifying the custom header parameters and response object. Then, test for errors by changing the fetch URL and observing the error handling. Finally, test the Page Visibility API by minimizing and maximizing the browser window.
By leveraging Fetch Event Source, developers can create dynamic applications with seamless user experiences, unlocking the power of real-time data.