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Learn how to solve the `connection(...).execute is not a function` error in your Express.js application when integrating with MySQL using `mysql2/promise`.
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This video is based on the question https://stackoverflow.com/q/67184537/ asked by the user 'david stephen' ( https://stackoverflow.com/u/11915478/ ) and on the answer https://stackoverflow.com/a/67184596/ provided by the user 'wrangler' ( https://stackoverflow.com/u/5115872/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Properly Use mysql2/promise in Express Routes

When working with Node.js and Express, you often need to perform database operations. One popular library for MySQL is mysql2/promise, which allows you to work with promises for better asynchronous code. However, you may encounter an error stating that connection(...).execute is not a function. This can be confusing, especially if you're certain the function is defined. Let's dive into how to correctly implement mysql2/promise in your Express routes and resolve this error.

Understanding the Problem

The error message you might see looks like this:

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

This issue arises when you attempt to use the .execute method on the result of your connection function without properly handling the asynchronous nature of Node.js.

The Connection Function

Here's a look at how the connection function is set up in the provided example:

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

The connection function is an asynchronous function that establishes a connection to a MySQL database. It returns a promise that resolves into a connection object.

The Route Setup

The route where the error occurs looks like this:

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

In this route, you're immediately trying to call .execute on the result of connection(), which hasn't been awaited yet.

Solution: Correctly Handling Promises

To fix the error, you need to ensure that you await the connection() function before trying to call .execute. Here are two ways to do this:

Option 1: Single Await Statement

You can combine the two await statements into one:

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

Option 2: Store Connection in a Variable

Alternatively, you can store the connection in a variable first and then use that variable to call .execute:

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

Conclusion

By properly awaiting the connection to your MySQL database, you can avoid the connection(...).execute is not a function error. Whether you choose to do this in a single line or by storing the connection in a variable, both methods will work effectively.

Key Takeaways:

Always remember to await your asynchronous functions, especially when dealing with Promises.

Understand the structure of your database connections in Node.js when using libraries like mysql2/promise.

With these adjustments, your Express routes should now function seamlessly with MySQL.

If you have any questions or run into other issues, feel free to leave a comment!