How to Execute Functions After Async Data Load in JavaScript

Discover how to tackle the challenge of executing functions after asynchronous data has finished loading using async/await in JavaScript.
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How to Execute Functions After Async Data Load in JavaScript

As web development evolves, many developers encounter challenges while managing asynchronous operations. One commonly faced situation is ensuring that specific functions execute only after all required asynchronous data has been fully loaded. If you find yourself dealing with a case where you need to run a function after multiple JSON files have been fetched, like with parsejson in JavaScript, this guide is for you.

The Problem: Asynchronous JSON Loading

When dealing with multiple JSON files, such as machines, classes, and subclasses, you may run into an issue where your main function fails because the data hasn’t loaded completely. If you attempt to run a function, such as get_parts(), before the data is ready, you'll likely experience unexpected errors.

Example Scenario

Let’s take a look at the original code setup and where the problem arises:

[[See Video to Reveal this Text or Code Snippet]]

In this example, the functions parsejson for loading JSON data are called, but get_parts is executed immediately afterwards. This creates a race condition where get_parts() is potentially trying to access data that hasn’t been fully loaded yet.

The Solution: Using Async/Await

To resolve this, you can leverage the async/await syntax introduced in ES2017. This approach allows you to write more readable asynchronous code, reducing the complexity that often arises from callbacks and promise chains.

Step-by-step Implementation

Modify the parsejson function: You need to make parsejson return a promise, which will resolve when the JSON data has been fetched.

Await JSON Loading: Use the await keyword before calling parsejson. This will make the asynchronous call pause until the data is fully loaded.

Here’s how to implement the solution:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of Key Changes

Declaration of Async Functions: Both parsejson and get_parts are declared as async. This allows the use of the await keyword within their body.

Awaiting Data Fetching: Each call to parsejson uses await, ensuring that the function does not continue until the respective JSON has been fully loaded.

Simple Structure: The revised approach makes the code cleaner and easier to follow as it removes nested callbacks.

Conclusion

By utilizing the async/await functionality in JavaScript, you can effectively manage the asynchronous loading of data and ensure that all necessary tasks are performed in the correct order. This greatly improves the reliability and readability of your code, while reducing potential errors caused by premature execution.

With this solution in hand, you can confidently tackle any similar issues in your own projects!