How can I make a type of the anonymous function?-CodePudding

The function that I want to make a type is below (a part of scratch-parser):

module.exports = function (input, isSprite, callback) {
    // Unpack the input and further transform the json portion by parsing and
    // validating it.
    unpack(input, isSprite)
        .then(function (unpackedProject) {
            return parse(unpackedProject[0])
                .then(validate.bind(null, isSprite))
                .then(function (validatedProject) {
                    return [validatedProject, unpackedProject[1]];
                });
        })
        .then(callback.bind(null, null), callback);
};

I created a type for this function, but the function is anonymous, so I cannot assert the type.

declare function scratchParser(
  input: Buffer | string,
  isSprite: boolean,
  callback: (
    err: Error,
    project: ScratchParser.Project | ScratchParser.Sprite,
  ) => void,
): void;

How can I assert the type of anonymous function by module.exports?

CodePudding user response：

Using declare isn't quite right, because that indicates that a function with that name exists in the JavaScript. But what you want is a type for the module.exports function to be compared to - or to satisfy.

Make scratchParser a type, and indicate that the exported function satisfies that type.

type scratchParser = (
  input: number | string,
  isSprite: boolean,
  callback: (
    err: Error,
    project: ScratchParser.Project | ScratchParser.Sprite,
  ) => void,
) => void;

module.exports = function (input, isSprite, callback) {
    // Unpack the input and further transform the json portion by parsing and
    // validating it.
    unpack(input, isSprite)
        .then(function (unpackedProject) {
            return parse(unpackedProject[0])
                .then(validate.bind(null, isSprite))
                .then(function (validatedProject) {
                    return [validatedProject, unpackedProject[1]];
                });
        })
        .then(callback.bind(null, null), callback);
} satisfies scratchParser;
// ^^^^^^^^^^^^^^^^^^^^^^