When you compare synchronous and asynchronous approaches in JavaScript, their practical differences become clear. Consider the synchronous code sample from earlier: each line waits for the previous one to finish before running. If a task takes a long time—such as reading a large file or waiting for a network response—the entire program pauses at that point. This means your application can become unresponsive to users if a slow operation is in progress.

By contrast, the asynchronous code schedules time-consuming operations to run in the background. While those tasks are being handled, the rest of your code continues to execute. For example, if you request data from a server asynchronously, your program can keep responding to user input or perform other work while it waits for the data. The result is a smoother, more interactive experience for users, especially in web applications where delays can be noticeable.