How to Create a Typescript Object Definition from an Array of Keys

Discover how to turn an array of strings into a well-typed `Typescript` object with clear properties in this comprehensive guide.
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Transforming an Array of Strings into a Typed Object in TypeScript

Creating a structured object from an array of strings in TypeScript can seem challenging, especially when you're focused on maintaining strong type definitions. This guide will walk you through a commonly encountered problem and will provide you with an effective solution to transform an array of keys into a well-typed object.

The Challenge: Object Creation from Array of Strings

Imagine you have an array of strings representing keys, and you want to convert this array into an object, where each key has a default value. For example:

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However, you may find that simply creating an object in TypeScript doesn't give you the expected types. This is where the problem arises: defining the type of the resultant object correctly.

The Solution: Strong Typing with Generics

To create a properly typed object from an array of keys, you can leverage TypeScript's generics. Here's how you can do it step by step.

Step 1: Define the Function with Generics

You can start by defining a function that takes an array of strings and uses a generic type parameter to ensure strong typing throughout the function. The key here is to define the parameter using Key extends string.

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Step 2: Implement the Logic

In this function:

keys: Key[] defines the input parameter as an array of strings.

reduce method is used to iterate over the array and accumulate the result.

Record<Key, boolean> is used to define the type of the resulting object. This ensures that the keys of the object are strictly typed based on the input array.

Step 3: Using the Function

You can easily use this function with various arrays of strings. For instance:

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The resultant type will be { "foo": true, "bar": true }, as expected.

Summary

In summary, using TypeScript to create a typed object from an array of strings can be efficiently achieved by employing generics and the Record utility type. This not only helps maintain type integrity but also makes your code cleaner and easier to read. The defined function ensures that each key from your input array accurately represents a property on the returned object, with the expected boolean value.

This approach can streamline your coding process significantly, allowing for better maintainability and fewer errors when working with dynamic object structures in TypeScript.

If you find yourself needing to perform this operation often, consider storing this utility function for quick access in your TypeScript toolkit.