Port to TypeScript

[Sumolari]

I've ported the entire library to Typescript and added proper type definitions so when the library is loaded the editor can know the types.

It's been tested with VSCode and works fine. Exported package will include Typescript definitions in .d.ts files as well as ES5 .js files.

This closes #4.

[coveralls]

Coverage increased (+1.8%) to 93.636% when pulling 5df9c98 on 4-Port-to-TypeScript into 7e6b4e1 on master.

[coveralls]

Coverage increased (+1.8%) to 93.636% when pulling 5df9c98 on 4-Port-to-TypeScript into 7e6b4e1 on master.

[furstenheim-geoblink]

can't this be defined also on a map?

[Sumolari]

Yes but it's already covered in the Lodash module declaration.

You can't have multiple functions with the same name in Javascript. However, it's possible to have mutliple functions with the same name but different signature (parameters types) in TypeScript.

To achieve this TypeScript forces you to have only one implementation for that function but allows you to expose several signatures.

So when you see a 5 different possible _.map functions you are seeing 5 signatures for the very same implementation.

Here if we allow using Dictionaries as well as Arrays then user would be able to use types for which the underlying functions are not defined, for instance, an ArrayIterator used to map an Dictionary.

Lodash solves this by declaring completely different signatures for Arrays, Lists, Dictionaries and so on.

I've decided that, as users are going to use the signatures exposed in Lodash object, that's offering proper signatures there is goo enough. It's true that if you import the underlying method directly it won't allow you to use all the combinations allowed when using the mixin. However, that's not really a problem since the implementation is not designed to be used outside of a Lodash mixin.

[fofi]

Aren't test/e2e/index.spec.ts and this file exactly the same?

[Sumolari]

Not exactly, test/e2e/index.spec.ts is loading the built package (from dist folder) while test/integration/index.spec.ts is loading the index from src folder

[dpramar]

Why is the definition different here than in other files? where we have

CollectionItem extends any,
  Collection extends ArrayLike<CollectionItem | null | undefined>,
  PropertyName,
  TResult
> (
collection: Collection,
iteratee: ObjectIterator<CollectionItem, [PropertyName, TResult] | null | undefined>

we should have consistency.

[Sumolari]

Because the definition of _.map forces us to be more strict. If we use a more generic definition then the compiler wrongly matches our _.map usage to the one of using an Object as iteratee, which always returns an array of boolean (boolean[]) which is not allowed by _.fromPairs.

It's tricky because Lodash types are really complex but I think this is good enough (see also this comment about why types of those methods are not really so important)