ts-guideline

Minimalistic configuration for TS to only extend JS with types. No TS-scpecific features, no bundling. Readable maintainable code after compilation.

• commonjs folder for CommonJS Modules ts-configuration compatible with ECMAScript import

• ecmascript folder for ECMAScript Modules ts-configuration

• js-dts folder for JS + DTS configuration.

• js-doc folder for JS Doc + TypeScript configuration

Important: use different file names sum.js - isum.d.ts to not create import conflicts

Reccomendations

1. Avoid using type aliases - example from mongoose types

   export type ApplyBasicQueryCasting<T> = T | T[] | (T extends (infer U)[] ? U : any) | any;

   this is unreadable and overcomplicated

   Aliases are good only for simple types

   type Fruit = 'banana' | 'orange' | 'pineapple' | 'watermelon';
   
   type Debt = { amount: number; dueTo: Date };
   type AccountDebt = { accountId: number; debt: Debt | null };

2. Never use complicated generic types - example from mongoose types

   type QueryWithHelpers<ResultType, DocType, THelpers = {}, RawDocType = DocType> = Query<
     ResultType,
     DocType,
     THelpers,
     RawDocType
   > &
     THelpers;

   basically it looks worse then

   type QueryWithHelpers<any> = Query<any> & any;

3. Not everything is neccessary to cover with types.

   It requires to add useless interfaces for type like this. Better just not use this.

   // with typing
   interface IDynamicGeneratedClass {}
   
   const classGenerator = (): IDynamicGeneratedClass =>
     class DynamicGeneratedClass implements IDynamicGeneratedClass {
       args: number[];
       constructor(...args: number[]) {
         this.args = args;
       }
     };

   // simplified
   const classGenerator = () =>
     class DynamicGeneratedClass {
       args: number[];
       constructor(...args: number[]) {
         this.args = args;
       }
     };

4. avoid using any - there is no point at all to use typescript if you need to keep using any.

This list will continue in future.

Alternatives

1. You can use JS Doc @type for type definitions, typescript will work and check types for you

2. You can always use JS + DTS - it is a similar way as it is done in C++ with .h and .cpp files DTS files are not working perfectly. Sometimes you forced to use JS Doc @typedef to import types from d.ts files

Summary

I prefer to use JS + DTS or JS DOC + TypeScript, because it solve every type issues, but not requires to write code in TypeScript

If it is not possible for you to follow this 2 solutions, please think about using those TS Guidelines. It will reduce your pain in the future.

TypeScript will sync their development within the JavaScript standard. This means there will be no TS Decorators and TypeScript will become more like JS Extension rather than a different language transpiled to JS.

Talk about Types and JS/TS future: