How to Use Node.js, TypeScript, and Express to Build a Web Server

TypeScript is a strongly typed programming language that is built on top of JavaScript. JavaScript is increasingly used in complex web applications with large codebases. Since you can use TypeScript anywhere that JavaScript is supported, you can replace JavaScript for TypeScript to reap the benefits of a strongly typed language. TypeScript enables developers to build applications quickly and with less errors. Some benefits of TypeScript are:

• Reduction of misspelled functions and properties
• Ensures that you use the correct argument types and number of arguments with functions
• Provides smarter autocomplete suggestions when working in your IDE

This guide shows you how to use TypeScript with two tools that are commonly used to build JavaScript web applications — Node.js and Express. Node.js provides a JavaScript runtime to use with web applications. Express offers a minimalist web framework to simplify building the various components of a web application. In this guide, you learn how to create a simple web server using TypeScript, Node.js, and Express.

The majority of the steps in this guide are performed on your computer’s local development environment. The following sections show you how to install TypeScript, Node.js, Express, and package dependencies on your computer. Any additional configuration steps required by each tool are also covered.

Note

If you do not have Node.js and the node version manager (nvm) installed on your computer, follow our How to Install and Use the Node Version Manager NVM guide. The steps in this guide require a minimum Node.js version of 13.0.0.

1. In your home directory, create a new directory named typescript-nodejs and move into the new directory.

    mkdir typescript-nodejs && cd typescript-nodejs
   

2. Create a package.json file for your project using the npm init command. The -y option generates the package.json file.

    npm init -y
   

   Your directory should now have a package.json file with the following contents:

   File: package.json

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   { "name": "typescript-nodejs", "version": "1.0.0", "description": "", "main": "index.js", "scripts": { "test": "echo \"Error: no test specified\" && exit 1" }, "keywords": [], "author": "", "license": "ISC" }

   This file provides information about the web server that you can update later. The most important entry is "main": "index.js". This defines the name of the main JavaScript file used to create the web server.

   The "license": "ISC" entry specifies that the license used for this web server is from the Internet Systems Consortium (ISC). To learn more about each key and value, refer to NPM’s documentation.

3. To avoid error messages in the next section of this guide, update the package.json file’s description key as follows:

   File: package.json

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   ... "description": "This is a test web server.", ...

   Note

   There is also a field defined in the package.json file called the repository field. You don’t have to provide a value for this field if you don’t have a repository configured to store your code.

4. Use npm to install Express with the command below. Ensure you are still in the typescript-nodejs directory when running the command.

    npm install express
   

   Since you don’t have a repository field defined in the package.json file, you see the following output:

   npm notice created a lockfile as package-lock.json. You should commit this file.
   npm WARN typescript-nodejs@1.0.0 No repository field.
   
   - express@4.17.1
   added 50 packages from 37 contributors and audited 50 packages in 2.539s
   found 0 vulnerabilities
       

   The first line of the output means that you should copy your package-lock.json file to your code repository. Typically, this is the repository you would point to in the package.json file’s repository field.

   If you inspect the package-lock.json file, you see a detailed description of the node_modules tree and package.json file. This file is automatically generated whenever npm modifies these two elements. You don’t need to worry about it for this guide, but there is a good discussion of it available in npm’s documentation. The remaining lines tell you about the version of Express that was installed and its details.

5. Install TypeScript using the command below. Even if you currently have TypeScript installed on your system, you need to install it again with the dependencies required to create this sample webserver project.

    npm install typescript ts-node @types/node @types/express --save-dev
   

   The ts-node part of the installation command installs ts-node, which is an execution engine for TypeScript and a Read–Eval–Print Loop (REPL) for Node.js. The @types/node and @types/express additions provide type definitions for TypeScript when interacting with Node.js and Express.

   Finally, the --save-dev command line switch indicates that TypeScript is only used for development purposes. Because you compile the TypeScript code to JavaScript, there is no dependency on TypeScript at runtime.

   When you execute the command, you see an output similar to the following:

   npm WARN typescript-nodejs@1.0.0 No repository field.
   
   - @types/express@4.17.13
   - ts-node@10.1.0
   - @types/node@16.4.7
   - typescript@4.3.5
   added 23 packages from 121 contributors and audited 74 packages in 4.338s
   found 0 vulnerabilities
   
       

   The output displays the repository warning again. Otherwise, information is returned about the version of TypeScript installed and how it interacts with Express.

At this point, you should have all requirements and dependencies installed in your development environment. In this section, you create the tsconfig.json file. This file is required at the root of a TypeScript project. It specifies directory information about the project and compiler options needed during compilation.

• Use the following command to create the tsconfig.json file.

    npx tsc --init
  

  The tsconfig.json file is created with the following content:

  File: tsconfig.json

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  { "compilerOptions":{ /*Language and Environment*/ "target":"es5", /* Modules */ "module":"commonjs", //"rootDirs": [], /* Interop Constraints */ "esModuleInterop": true, "forceConsistentCasingInFileNames": true, /* Type Checking */ "strict": true, /* Completeness */ "skipLibCheck": true /* Emit */ //"outFile": "./", //"outDir": "./", } }

  Note

  When the tsconfig.json file is created, several options are commented out. You can leave the settings as they are, but for more complex project, you can uncomment the necessary settings.

  The generated tsconfig.json file contains various default settings. You can learn more about each setting in TypeScript’s TSConfig Reference documentation. Unless you have reasons to change the target and module settings, you should leave those as they are defined. Likewise, keep strict set to true to ensure that your application uses strict type checking. Also, keep esModuleInterop set to true to ensure that you obtain full interoperability.

• For this example, you don’t have to change the settings listed below, but you’d likely need to do so for a large project.

  • rootDir: Specifies the location of the TypeScript files.

  • outFile: Concatenates and emits the webserver code to a single file. This is useful for small web servers and does provide a performance boost in some cases.

  • outDir: Specifies where you want the generated JavaScript to be stored after compilation.

Now that your development environment is completely configured, you’re ready to write some code and run it. In this section, you create a simple web server.

1. Ensure you are still in the typescript-nodejs directory. Create a new file named index.ts and add the following code to the file.

   File: index.ts

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   import express from 'express'; const app = express(); app.get('/', (req, res) => { res.send('This is a test web page!'); }) app.listen(3000, () => { console.log('The application is listening on port 3000!'); })

   The web server implementation is very basic, however, it provides a foundation to help you build something more complex. The above code imports express and instantiates a copy of express() as the app constant. This constant can be used to interact with your application.

   The call to app.get() specifies that the web server will respond to a root directory ('/') request with a message that reads This is a test web page!. Refer to the Express documentation to learn more about its routing features.

   The call to app.listen() describes what port to use when listening for requests. Whenever you start the application on the command line, you see the message The application is listening on port 3000!.

2. Run your code to create the webserver.

    npx ts-node index.ts
   

3. Navigate to a browser to view the site running on the localhost. Enter localhost:3000 as the URL. You should see the message This is a test web page! returned in your web browser’s session.

   To stop the webserver, press Ctrl+C at the command line.

When you use TypeScript to build a web application, you get the benefits of stricter programming language that is interchangeable with JavaScript. When using Express and Node.js with TypeScript your code is mush less error prone and verbose. Their benefits allow you to spend more time creating your web application’s features. If you are a JavaScript programmer, refer to the TypeScript for JavaScript Programmers tutorial to learn more about the differences between the two languages. If you are newer to TypeScript, you can refer to our guides on TypeScript classes, decorators, functions, and types.

More Information

You may wish to consult the following resources for additional information on this topic. While these are provided in the hope that they will be useful, please note that we cannot vouch for the accuracy or timeliness of externally hosted materials.

• npm documentation
• Express documentation
• TypeScript’s TSConfig Reference documentation