TypeScript Tip #3: Folder-wise config

The file tsconfig.json indicates that the project is using typescript. It specifies the different options required to compile the project.

There are situations when you are working on a huge project and migrating it from JavaScript to TypeScript. While new code is well-typed the older code is in a state where type-checking can not be as strict.

The need arises for different levels of type strictness in different sub-folders of the same project. This can be achieved using multiple config files.

Example: You do not allow the type any in your new subfolder. But the rest of your project being much legacy, still uses any here and there.

You can have "noImplicitAny": false in your main config file.

Inside the new subfolder, you can have another tsconfig.json file, which extends the main tsconfig.

{
  "extends": "../../../tsconfig.json",
  "compilerOptions": {
    "noImplicitAny": true
  },
  "include": ["*"]
}

This is a game changer for huge projects and allows for agile development.