Is there a way to combine two arrays of objects that may be undefined?

Question

Is there a way to combine two arrays of objects that may be undefined?

Here is the object I am working with:

interface Cart {
    orderPromo?: ProductPromotion[],
    productPromo?: ProductPromotion[],
}

Both properties are of the same type, but they can be undefined. What is the most efficient and clean way to merge them?

I initially attempted the following:

const promotions: ProductPromotion[] = [...cart.orderPromo, ...cart.productPromo];

However, this code resulted in an error message:

TS2488: Type 'ProductPromotion[] | undefined' must have a '[Symbol.iterator]()' method that returns an iterator.

typescript

Answer 1

Answer №1

When it comes to optional properties, the value of cart.orderPromo can either be an array of ProductPromotion or undefined (as per the error message). In the scenario where it turns out to be undefined, using the spread operator ...cart.orderPromo is not feasible.

To handle this situation, it is recommended to convert these properties to empty arrays if they happen to be undefined. This can easily be achieved with the help of the null coalescing operator ??:

const promotions: ProductPromotion[] = [...cart.orderPromo ?? [], ...cart.productPromo ?? []];

Answer 2

When it comes to optional properties, the value of cart.orderPromo can either be an array of ProductPromotion or undefined (as per the error message). In the scenario where it turns out to be undefined, using the spread operator ...cart.orderPromo is not feasible.

To handle this situation, it is recommended to convert these properties to empty arrays if they happen to be undefined. This can easily be achieved with the help of the null coalescing operator ??:

const promotions: ProductPromotion[] = [...cart.orderPromo ?? [], ...cart.productPromo ?? []];

Answer 3

Answer №2

The issue at hand is the uncertainty of whether cart.orderPromo or cart.productPromo is undefined in the TypeScript code. To address this, it is recommended to check for their existence before attempting to merge them. Utilizing optional chaining operator ?. allows for safe property access, and the Nullish Coalescing operator ?? can be used to assign a default empty array if needed.

Here's an example:

const promotions: ProductPromotion[] = [
  ...(cart.orderPromo ?? []),
  ...(cart.productPromo ?? [])
];

Answer 4

The issue at hand is the uncertainty of whether cart.orderPromo or cart.productPromo is undefined in the TypeScript code. To address this, it is recommended to check for their existence before attempting to merge them. Utilizing optional chaining operator ?. allows for safe property access, and the Nullish Coalescing operator ?? can be used to assign a default empty array if needed.

Here's an example:

const promotions: ProductPromotion[] = [
  ...(cart.orderPromo ?? []),
  ...(cart.productPromo ?? [])
];

Is there a way to combine two arrays of objects that may be undefined?

Answer №1

Answer №2

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