Explanation of returning multiple values

Question

Explanation of returning multiple values

Can you help me understand how to specify the type when a function returns two values?

Consider this function:

const exampleFunction = (input: number) => {
  const firstValue = input;
  const innerFunction = (funcInput: number) => {
    funcInput * input;
  };
  return [firstValue, innerFunction];
};

Here is how I am calling it:

const [value, innerFunction] = exampleFunction(1);

However, TypeScript seems uncertain whether innerFunction is actually a function. Currently, it interprets it as:

number | ((funcInput: number) => void)

Is there a way to inform TypeScript that the second return value is indeed a function?

typescript

Answer 1

Answer №1

In order to achieve that task efficiently, you must ensure your function returns a tuple type:

To accomplish this, define your function like so:
const myFunc = (input: number): [number, (funcInput: number) => void] => { ... };
                                    // ^-----------------------------------^

Answer 2

In order to achieve that task efficiently, you must ensure your function returns a tuple type:

To accomplish this, define your function like so:
const myFunc = (input: number): [number, (funcInput: number) => void] => { ... };
                                    // ^-----------------------------------^

Answer 3

Answer №2

To improve readability, consider creating a custom type or interface for the return value:

interface CustomType {
    value: number;
    action: (num: number) => void
}

const myFunction = (input: number): CustomType => { ... }; // The return structure will be clearer

You can also directly specify the return type in the function:

const myFunction = (input: number) => {
// ...
return {
      data,
      action
   }
};

Using tuples may not provide clear field names since they are position-based.

It's recommended to choose an approach that includes descriptive field names to avoid confusion.

Answer 4

To improve readability, consider creating a custom type or interface for the return value:

interface CustomType {
    value: number;
    action: (num: number) => void
}

const myFunction = (input: number): CustomType => { ... }; // The return structure will be clearer

You can also directly specify the return type in the function:

const myFunction = (input: number) => {
// ...
return {
      data,
      action
   }
};

Using tuples may not provide clear field names since they are position-based.

It's recommended to choose an approach that includes descriptive field names to avoid confusion.

Explanation of returning multiple values

Answer №1

Answer №2

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