[00:00] One thing you'll notice about our client and server setup here is we have two tsconfig.json files and they're both pretty similar. They actually have pretty much exactly the same config all up here except for the server has an extra attribute called lib.

[00:14] It would be really great if we could make a root tsconfig.json file which they could both inherit from. For this we're going to need the extends property inside the tsconfig.json inside the root ones and we're going to have to create a tsconfig.base.json to inherit from.

[00:33] That is the task. Good luck!


We have been working with separate `client` and `server` `tsconfig.json` files, but they are almost identical. The only difference is that the server configuration has an extra `lib` attribute:

```tsx
// client/tsconfig.json
{
  "compilerOptions": {
    "target": "ES2022",
    "module": "ESNext",
    "moduleResolution": "Bundler",
    "esModuleInterop": true,
    "noEmit": true,
    "strict": true,
    "skipLibCheck": true,
    "isolatedModules": true
  }
}

// server/tsconfig.json
{
  "compilerOptions": {
    "target": "ES2022",
    "module": "ESNext",
    "moduleResolution": "Bundler",
    "esModuleInterop": true,
    "noEmit": true,
    "strict": true,
    "skipLibCheck": true,
    "isolatedModules": true,
    "lib": [
      "ES2022"
    ]
  },
}
```

In order to reduce redundancy, it would be better if we could create a root `tsconfig.base.json` file that both client and server could inherit from.

## Challenge

Your task is to create a `tsconfig.base.json` that contains the shared configuration, and modify the existing `tsconfig.json` files in the client and server directories to extend this base configuration.

Hint: Look into the `extends` property for `tsconfig.json` files, and note that the path to the base file is resolved relative to the extending `tsconfig.json`.

Make your TypeScript configuration more maintainable by creating a shared tsconfig.base.json file.

[00:00] In the solution here, we have created a tsconfig.base.json. This could be named anything we want to. I kind of just like calling it .base.json because it indicates, first of all, that it's not a working tsconfig. So TypeScript itself won't look at this and go, ooh, I need to use this to reference

[00:18] all of the other TypeScript files. It will pass over it. But we can use it to basically say, inside the client here, we can say that this tsconfig.json, which is something that TypeScript will check, extends this tsconfig.base.json, which lives above it. So this one will just inherit

[00:36] all of the compiler options inside here. Inside the server, too, we basically do the same thing, but we just add in our extra compiler options that we need here. Beautiful stuff. Now, this works really nicely when you have, let's say, a monorepo, so many, many tsconfigs that you all need

[00:55] to reference basically a single one. And this means that you can change a single value inside here, so restrict or no emit or whatever you like, and you can just basically make that inherit throughout the entire project. You can even have multiple of these. For instance, if you're operating in different environments, that's very, very common, too. So the extends property is really nice.

[01:14] Now, make sure, though, that when you do this, that extends, like, extends will only copy the compiler options over, I'm pretty sure. So anything outside of this, like exclude, or like include, for instance, which lets you specify the files that you want to add into your TypeScript compilation, I'm pretty sure they won't be added. It's mainly just for compiler options.

[01:33] But extends, very, very useful in these situations where you have lots of tsconfigs that you just want to have a base version of and then add extra properties to as you need them.


We'll start by creating a `tsconfig.base.json` file, which serves as our base TypeScript configuration.

It's important to note that this is not a working configuration file for TypeScript, and it will not be used to directly reference other TypeScript files. Instead, it acts as a base configuration that other `tsconfig.json` files can extend.

The `tsconfig.base.json` file contains all the compiler options that are common to both the client and server configurations:

```tsx
{
  "compilerOptions": {
    "target": "ES2022",
    "module": "ESNext",
    "moduleResolution": "Bundler",
    "esModuleInterop": true,
    "noEmit": true,
    "strict": true,
    "skipLibCheck": true,
    "isolatedModules": true,
  },
}
```

Then inside of the `tsconfig.json` file in the `client` directory, we'll use the `extends` keyword to specify that it extends `tsconfig.base.json`. Remember, the files are resolved relative to the extending `tsconfig.json` file, so we need to use `../../` to go up two directories:

```tsx
// client/tsconfig.json
{
  "extends": "../../tsconfig.base.json"
}
```

We do the same in the `server` directory, but with additional compiler options:

```tsx
// server/tsconfig.json
{
  "extends": "../../tsconfig.base.json",
  "compilerOptions": {
    "lib": [
      "ES2022"
    ]
  },
}
```

By extending the base configuration, these `tsconfig.json` files inherit all the compiler options from `tsconfig.base.json`.

This approach is particularly useful when working with monorepos, where many `tsconfig.json` files need to reference a single base configuration.

Another benefit of this setup is that it allows you to change a single value in the base configuration and have that change propagate throughout the entire project.

It's important to note that the `extends` property only copies over `compilerOptions` from a `tsconfig.json` file. Other properties like `exclude` or `include`, which specify the files to include in or exclude from TypeScript compilation, won't be added.

If you're using a monorepo, this approach is highly recommended!

Learn how the extends property in TypeScript configuration files helps reduce redundancy.

Extending a Base TypeScript Configuration

Share Configuration Across Multiple tsconfig Files

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Share Configuration Across Multiple tsconfig Files

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