Salesforce JavaScript Developer Practice Exam 2025 - Free JavaScript Developer Practice Questions and Study Guide

The distinction between synchronous and asynchronous code is fundamental to understanding how JavaScript operates, particularly in relation to how it handles operations such as I/O tasks, network requests, and timers.

Synchronous code executes in a manner that each operation is completed before the next one begins. This means that if a synchronous function is running, the program will wait until that function has finished executing before moving on to the next piece of code. This can lead to a blocking effect, where if one part of the code takes a long time to execute, it hampers the overall performance and responsiveness of the application.

On the other hand, asynchronous code is designed to allow certain operations to occur independently, meaning that the execution of other code can continue while waiting for the asynchronous operation to complete. For example, if you make a network request, the program doesn't halt; instead, it can proceed to execute other tasks. Once the network request is completed, a callback function or promise can be used to handle the result of that request. This non-blocking behavior is essential for building responsive applications, particularly in environments such as web browsers, where user experience is paramount.

Other provided options touch on misconceptions. Although some might assume that asynchronous code might inherently be slower, it actually allows for