Creating an array that exclusively contains numbers using anonymous object export: A step-by-step guide

I am struggling with a record that is designed to only accept values of type number[] or numbers.

This is how it is structured:

type numberRecords = Record<string,number[]|number>;

I ran into an error when trying this:

export const myList:numberRecords = {
    a: ["a",2]
}

However, I encountered no issues with the following code:

export default <numberRecords> {
    a: ["a",2]
}

I can't understand why this happens. Should I use a named object or stick with an anonymous, default object? Personally, I would prefer the latter option...

typescript

Answer №1

When utilizing the <numberRecord> in TypeScript, you are essentially telling the compiler: "I am aware of what I am doing, please ignore any potential type warnings and assume that the object is of type numberRecords.

This is akin to:

export default {
    a: ["a",2]
} as numberRecords;

Both of these methods can be risky - only resort to using as or <someType> for type assertion when there are no other alternatives, otherwise your code's typings may not be secure, as demonstrated here.

In contrast, by employing:

const someVariableName: someType = ...

you are indicating to the compiler that someVariableName must adhere to someType (and if it fails to do so, TypeScript will throw an error). This method is much safer.

If you wish to proceed in this manner, it is advisable to declare the variable and its type beforehand, then export it as default:

const myList: numberRecords = {
    a: ["a",2]
};
export default myList;

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