# Setting up a Project with Express and TypeScript

### Bare minimum Typescript Setup

1.  first make a folder and `npi init`
    
2.  run `tsc --init`
    
3.  change root directory on `tsconfig.json` file :  
    "rootDir": "./src",  
    "outDir": "./dist",  
      
    (/dist = distributable file)
    
4.  to compile `tsc -p .` YOU NEED TO DO IT EVERY time you make some changes to your code
    
5.  to run `node /dist/filename.js`
    
6.  make .gitignore file and add ( dist/, node\_modules/ , .env)  
    and run `npx gitignore Node`
    
7.  even if you have typscript installed on your machine globally, it is good idea to instal typescript in your project too. (Better install as dev dependency)  
      
    `npm i typescript -D`
    
8.  to get rid of problem described in number 4 .. install  
    `npm i tsc-watch -D`  
    and  
    set up a script dev as following:
    
    ```json
    "dev": " tsc-watch --onSuccess \"node dist/index.js\""
    ```
    
9.  you can change
    
    ```json
      "type": "module", //commonjs---> module
    ```
    

### Installing Express and Its Type Definitions in TypeScript

After setting up your TypeScript , you usually install Express like this:

```plaintext
npm install express
```

**But here’s the catch:** if you try to use Express in your `.ts` files immediately, TypeScript will complain:

```plaintext
Cannot find module 'express' or its corresponding type declarations.
```

This happens because **Express is written in plain JavaScript**, so TypeScript can’t automatically know the types of its functions, objects, or middleware.

There are two ways to fix this:

*   **Write your own types** – You can create type definitions (`.d.ts`) for the functions, objects, or methods you plan to use in Express. But this can be tedious.
    
*   **Install existing type definitions** – The easier way is to use the community-maintained types from npm. Packages with the `@types/` prefix are exactly for this.
    

```plaintext
npm i @types/express -D
```

Here’s what happens when you run this:

*   TypeScript now knows the structure of Express, including functions, request/response objects, and middleware.
    
*   Your editor (like VS Code) will give you **autocomplete, hints, and error checking** for Express code. any previous “Cannot find module” errors will disappear.
    

**Pro tip:** On the npm website, look at the **top-right corner of the package name**. If you see `DT` or `ts`, it means this package **includes TypeScript type definitions**.

**DT** → comes from **DefinitelyTyped**, the community-maintained repository of type definitions.  
**ts** → the package itself is written in TypeScript or includes its own types.

  
This is a quick way to check if a JavaScript library is TypeScript-ready before installing it.

### Node.js Type Definitions in TypeScript

TypeScript doesn’t know the types of Node’s built-in modules (`fs`, `http`, `path`, etc.) by default. To fix this, install the Node type definitions:

```plaintext
npm i -D @types/node
```

This lets TypeScript understand Node modules and provides **autocomplete, hints, and error checking** in your editor.