How to Call the Same Function Sequentially with Different Arguments Using setTimeout() in JavaScript

Discover a clean way to call a JavaScript function sequentially with different arguments, ensuring completion before the next call, without relying on static delays.
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How to Call the Same Function Sequentially with Different Arguments Using setTimeout() in JavaScript

When working with JavaScript, one common requirement is to execute a function multiple times, each with different arguments, while ensuring that each execution of the function completes before the next begins. This scenario is particularly common in asynchronous programming. Today, we’re going to explore how to handle this using setTimeout() in a more organized manner.

The Problem

Consider a situation where you have two arrays, arr1 and arr2, and you want to print each element of these arrays sequentially using a function called example(). The initial code snippet demonstrates an issue where the function example() does not wait for the previous execution to finish before starting the next one.

Here’s the relevant code snippet:

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

Expected Output

From the above code, the output you would get is interleaved like so:

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

However, our aim is to have the output in a sequential manner:

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

The Solution

To address this issue, we will leverage Promises and async/await syntax, which are part of modern JavaScript. This will allow us to let our asynchronous logic inform us when it’s finished, so that we can chain subsequent calls to our function.

Step-by-step Walkthrough

Modify the logic() Function:

We need to change the logic() function to return a Promise, indicating when the asynchronous operation (the setTimeout()) is complete.

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

Update the example() Function:

Make example() an async function and use await to ensure that we wait for the logic() function to complete before moving on to the next iteration.

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

Execute the Functions Sequentially:

Finally, we can sequentially call the example() function using an immediate async function setup that will first call example(arr1) and then example(arr2).

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

Complete Code

Here’s how the complete, improved code looks:

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

Conclusion

By using Promises and the async/await syntax, we have successfully created a mechanism to call the same function multiple times with different arguments sequentially. This avoids the pitfalls of static delays and ensures that our code remains clean and efficient. If you're working with asynchronous code in JavaScript, mastering these concepts will be incredibly valuable. Happy coding!