Understanding Asynchronous JavaScript: The Impact of Sequential Requests

In JavaScript development, handling asynchronous operations efficiently is crucial for optimizing performance and delivering a responsive user experience. When dealing with multiple asynchronous requests, the approach you choose can have a significant impact on your application’s performance. In this article, we’ll explore the consequences of making sequential requests without leveraging Promise.all.

The Problem with Sequential Requests

Imagine you have a web application that needs to fetch data from multiple endpoints. Without proper handling, these requests might be executed sequentially, meaning that each request waits for the previous one to complete before starting. This approach can lead to longer response times and slower overall performance, resulting in a less responsive user interface.

Let’s consider an example where we need to fetch data from two different APIs and process the results. Here’s how we might do it without using Promise.all.

const fetchData = async () => {
  const data1Response = await fetch('https://myapi1.com/data1');
  const jsonData1 = await data1Response.json();

  const data2Response = await fetch('https://myapi2.com/data2');
  const jsonData2 = await data2Response.json();
  .
};

In this example, each fetch request is made sequentially, meaning that the second request won't start until the first one completes. As a result, the overall execution time is increased, leading to slower performance and a less responsive application. Since each request’s response is independent of the others, these requests can be made concurrently. Let me show you how we can achieve this.

The Solution: Leveraging Promise.all

To overcome the limitations of sequential requests and improve performance, we can leverage Promise.all. This method allows us to execute multiple promises concurrently and wait for all of them to resolve. Here’s how we can rewrite the previous example using Promise.all.

const fetchData = async () => {
  const [data1Response, data2Response] = await Promise.all([
    fetch('https://api.example.com/data1'),
    fetch('https://api.example.com/data2')
  ]);

  const jsonData1 = await data1Response.json();
  const jsonData2 = await data2Response.json();
  
};

In this version, both fetch requests are executed concurrently using Promise.all, leading to faster execution times and improved performance.

Feel free to reach out to me for any doubt, Happy Learning :-)