What is the correct method for using typedef to define a function with the signature "() => void" in accordance with tslint guidelines?

Question

What is the correct method for using typedef to define a function with the signature "() => void" in accordance with tslint guidelines?

Currently, I am working on a function that requires specific typing:

const checkIfTagNeedsToBeCounted = (listOfTags: string[]): boolean => {
  const tagsToExcludeFromCounting: string[] = [
    "DoNotCount",
  ];

  const excludedTagFound: boolean = listOfTags.some(
    (singleTag) => tagsToExcludeFromCounting.includes(singleTag),
  );

  return !excludedTagFound;
};

However, when I try to define it with

const checkIfTagNeedsToBeCounted: Function = ...

I receive a warning from tslint:

Avoid using 'Function' as a type. It is recommended to use a specific function type, such as () => void. (ban-types)

While I have been temporarily silencing this issue with

// tslint:disable-next-line: ban-types
const checkIfTagNeedsToBeCounted: Function = (listOfTags: string[]): boolean => {

I am curious to learn the correct way of typing a function according to tslint?

typescript typescript-typings tslint

Answer 1

Answer №1

Function is not specific enough on its own.

TypeScript advises that you must precisely define the function's prototype for better results.

This will enable auto-completion and error detection for issues such as incorrect parameters, etc.

You have two options to address this: either let TypeScript infer the function type automatically,

or manually specify the type of the function yourself.

REMINDER: Opt for the second choice if TypeScript struggles to infer correctly (usually when using any extensively) or if you want to reuse the type definition.

In your scenario:

const checkIfTagNeedsToBeCounted: (listOfTags: string[]) => boolean = (listOfTags: string[]): boolean => {
   // ...
};

If you wish to reuse the function type :

type MyFunction = (listOfTags: string[]) => boolean;

const checkIfTagNeedsToBeCounted: MyFunction = (listOfTags: string[]): boolean => {
   // ...
};

Answer 2

Function is not specific enough on its own.

TypeScript advises that you must precisely define the function's prototype for better results.

This will enable auto-completion and error detection for issues such as incorrect parameters, etc.

You have two options to address this: either let TypeScript infer the function type automatically,

or manually specify the type of the function yourself.

REMINDER: Opt for the second choice if TypeScript struggles to infer correctly (usually when using any extensively) or if you want to reuse the type definition.

In your scenario:

const checkIfTagNeedsToBeCounted: (listOfTags: string[]) => boolean = (listOfTags: string[]): boolean => {
   // ...
};

If you wish to reuse the function type :

type MyFunction = (listOfTags: string[]) => boolean;

const checkIfTagNeedsToBeCounted: MyFunction = (listOfTags: string[]): boolean => {
   // ...
};

What is the correct method for using typedef to define a function with the signature "() => void" in accordance with tslint guidelines?

Answer №1

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