Solving the Error: await is only valid in async function in JavaScript with Puppeteer

Learn how to fix the `await is only valid in async function` error in your Puppeteer scripts by following proper asynchronous function practices.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Where is my synchronous function? Trying to call "await" but I get the error "await is only valid in async function."

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding the Issue: await is only valid in async function

If you're writing a script using Puppeteer to automate tasks like logging into websites or emulating various devices, you might encounter the frustrating error: await is only valid in async function. This error can hinder your progress, especially if you’re not familiar with how asynchronous programming works in JavaScript.

When you attempt to use await outside of a function declared with async, JavaScript won’t know how to handle the asynchronous call, leading to this syntax error.

Common Scenario

For instance, if your script includes multiple asynchronous functions to sequentially log in and navigate through URLs as different mobile devices, you may find yourself struggling with organizing your calls correctly.

Example of the Problematic Code

Here’s a simplified example of what might be going wrong in your code:

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

Why This Happens

The error likely arises because you’re trying to map through an array of devices and call login(), which itself uses await for asynchronous operations. A map() function does not play nicely with promises, as it executes the callback function for each item in the array concurrently rather than awaiting each operation to finish.

The Solution: Restructuring Your Asynchronous Code

To fix this issue, you’ll need to ensure that your functions are properly sequenced and that they communicate back to the caller about when they've completed. The following sections walk you through the necessary changes.

Step-by-Step Fix

Sequence the Operations: Ensure operations happen one after another, avoiding overwhelming your system’s resources.

Communicate Completion: Use return statements or logging to confirm when tasks are done.

Correctly Declare Strings: Double-check that you’re using template strings properly.

Use await with Promise Operations: Always await any asynchronous operations.

Replace Non-Promise Aware Methods: Instead of .forEach() or .map(), which do not work with promises, use a classic for loop.

Error Handling: Use try/catch blocks to handle errors gracefully without stopping all operations.

Revised Code Example

Here’s how you could rewrite your code to adhere to these best practices:

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

Key Changes Made

For Loop Usage: Replaced map() and forEach() with a for...of loop for proper sequencing.

Error Handling: Added catch to log any errors and allow the process to continue.

Closed the Browser: Remember to close your browsers to free up resources after each task.

Conclusion

By following these guidelines, you can effectively troubleshoot and resolve the await is only valid in async function error in your Puppeteer scripts. Structuring your asynchronous code properly not only resolves errors but also enhances the overall reliability and performance of your automation tasks.

Remember, async programming can be tricky at first, but with these techniques, you'll become proficient in no time!