[00:00] In general, in your front-end applications, you're gonna be using modules and not scripts. So it would be really good if there was a way to tell TypeScript that everything I do inside this project is a module, not a script. And if I have an accidental script here, let's say I have a script one file and a script two file, it would be great if I could get an error saying

[00:19] my func shouldn't be used without being imported. Your job is to try to go into the tsconfig.json for this folder and actually add an option on here that forces TypeScript to say, okay, everything is going to be a module, not a script.

[00:38] I will add a link below to the tsconfig option if you get a bit confused or if you get a bit lost, but try and see if you can navigate it yourself. Good luck.

In general, frontend applications will use modules instead of scripts.

Consider the following scenario with two files `script-1.ts` and `script-2.ts`:

```typescript
// script-1.ts
const myFunc = () => {
  console.log("Hello!");
};

// script-2.ts
// I can use myFunc without importing it!

// @ts-expect-error // red squiggly line under @ts-expect-error
myFunc();
```

Currently in this setup, `myFunc` from `script-1.ts` is accessible in `script-2.ts` without an import statement. 

This behavior is more characteristic of scripts than modules, which is not ideal for modern applications.

Instead, we want to enforce module usage so that `myFunc` can only be used in `script-2.ts` if it's imported from `script-1.ts`.

## Challenge

Your challenge is to modify the `tsconfig.json` file to ensure TypeScript treats all files in the project as modules.

This change should trigger an error if a function or variable from one file is used in another without proper import syntax.

Here's the existing `tsconfig.json`:

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

Hint: If you're unsure which option to modify or add, check out the [tsconfig Cheatsheet on totaltypescript.com](https://www.totaltypescript.com/tsconfig-cheat-sheet).

Learn how to configure TypeScript to treat all files as modules instead of scripts.

[00:00] Okay, we're looking to add an option to this TS config in order to make script two not show this error anymore, or make my func not available in the global scope. The way we can do that is with an option called module detection, and then there's a few options here. We can either have auto, force, or legacy.

[00:19] Auto is basically the default value, which is the behavior that we saw in the previous exercise, where it checks to see if there's an import and export, and force forces it to be a module. So now if we go into script one up here, we can see that my func is declared, but its value is never read.

[00:37] This is not being put into the global scope anymore, even though there's no import and export on it. And this TS expect error is now triggering because it says it cannot find name my func. So module detection force is something that I recommend pretty much in all cases when you're working on a module system,

[00:56] because you're gonna just like, it just more closely matches the environment that you're actually coding in, and there are various weird errors that you won't get anymore when you're just creating new files, for instance. So module detection force is part of my recommended TS config for all projects.

In order to update the `tsconfig.json` file so that TypeScript treats all files as modules, we need to add the `moduleDetection` option.

The `moduleDetection` option determines how functions and variables are scoped in your project. It comes with three settings: `auto`, `force`, and `legacy`. 

- `Auto`: This is the default setting. TypeScript checks for any `import` or `export` statements in a file and treats the file as a module if it finds any.
- `Force`: Forces TypeScript to treat all files as modules, even if they don't have `import` or `export` statements.
- `Legacy`: A backward-compatible mode that may not apply modern module scoping rules.

In our case, we want to use the `force` option:

```json
// tsconfig.json

{
  "compilerOptions": {
    // ...other options...
    "moduleDetection": "force"
  }
}
```

In our exercise, we used two scripts to demonstrate the effect of the `moduleDetection` setting.

With this update, the `myFunc` function in `script-1.ts` is no longer available in the global scope. This means that `script-2.ts` will throw an error if we try to call `myFunc` without importing it first.

```typescript
// script-1.ts

const myFunc = () => {
  console.log("Hello!");
};
```

The `@ts-expect-error` directive now works as expected:

```typescript
// script-2.ts

// @ts-expect-error
myFunc();
```

Using `moduleDetection: force` is recommended for projects using a module system. This setting aligns your development environment more closely with real-world scenarios and reduces unexpected errors, particularly in projects where new files are frequently created.

Adjusting the tsconfig.json file will force TypeScript to treat all files as modules instead of scripts.

Update tsconfig for Modules

Enforcing Module Usage in TypeScript

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Unexpected Token Error in the Browser

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Compile TypeScript to JavaScript with the TypeScript CLI

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Two Syntaxes for Arrays

Add an Array to an Object

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Representing an Array of Objects

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The `void` Type

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Enforcing Module Usage in TypeScript

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