How to Properly Export an Array in a .d.ts File in TypeScript

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Understanding the Problem

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You likely tried to follow this initial structure:

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However, this does not correctly declare the export in accordance with how the module was originally set up. You may also have experimented with trying to declare it as the default export with no success.

The Solution

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Let’s break down this solution for better understanding:

Step-by-Step Breakdown

Use export = for CommonJS Compatibility:

Declare the Constant:

The line declare const foobar: Ifoobar[]; properly defines the array type you are exporting. This tells TypeScript that foobar is an array of objects conforming to the Ifoobar interface.

Define the Interface:

The interface Ifoobar declaration allows you to specify the structure of each object within the foobar array. In this case, each object must have a foo property of type string.

Advantages of This Approach

Type Safety: By correctly declaring the export, TypeScript will now provide type safety while working with the foobar array across your application.

Conclusion

If you find yourself needing to type an exported array, keep this guide handy, and you'll be less likely to run into issues in the future!