Resolving the TypeError: defineCall is not a function in Sequelize with Node.js

Learn how to troubleshoot the `TypeError: defineCall is not a function` error in your Sequelize setup, often caused by module import issues. Explore the curious case of ts-node-dev and find a straightforward solution to your problem.
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Understanding the Problem

You may have a well-structured Sequelize project, yet you are unable to import models without running into this error. The known error typically emerges under the following circumstances:

Your project is set up with TypeScript but you may be facing issues with require() when trying to import certain model files.

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The unfortunate part here is the line that attempts to import a model, which can lead to defineCall being undefined if not handled properly.

Root Cause Identification

The issue tends to arise when the code runs through the import function without defining defineCall. It tries to access an object or a function that does not exist at that moment. In your case, the problematic line of code looks like this:

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Here, defineCall expects to get a function that defines a Sequelize model, but it ends up being undefined. Why does this happen? The answer often lies elsewhere in your development environment, particularly in the version of tools you are using.

The Solution: Updating ts-node-dev

After some investigation into your specific case, it became clear that the problem was stemming from ts-node-dev. Ensuring this dependency is updated can resolve multiple import-related issues. Here's how you can tackle the problem:

Update ts-node-dev:

Run the following command to update ts-node-dev to the latest version in your project:

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In this scenario, updating from version 1.0.0-pre.49 to 1.1.6 resolved the issues you were facing.

Re-test Your Setup:

After updating, restart your application and check whether the TypeError: defineCall is not a function still appears. Most likely, it should be resolved now.

Conclusion

Hiccups are common in the world of coding, particularly when working with dependencies and module imports. The error you encountered, TypeError: defineCall is not a function, can often be traced back to version issues or environment inconsistencies. The simple update of ts-node-dev has proven to be the knight in shining armor for many developers facing this challenge.

If you encounter similar issues in your JavaScript and Sequelize work, don't hesitate to explore dependency updates as your first line of defense. Happy coding!