JavaScript to TypeScript

March 28, 2024
Sep 8, 2023


JavaScript has long been the go-to language for web development, powering dynamic and interactive web applications. However, as web development continues to evolve and become more complex, developers are seeking better ways to manage their codebases, prevent bugs, and increase productivity. This is where TypeScript comes into play. TypeScript, a statically-typed superset of JavaScript, offers numerous advantages that make it a great choice for developers looking to enhance their development workflow. In this article, we'll explore the reasons why developers should consider making the transition from JavaScript to TypeScript, and we'll also cover step by step how to migrate from JavaScript to TypeScript either manually or with an automated tool.

Why TypeScript?

Strong Static Typing

One of the most significant advantages of TypeScript is its strong static typing system. While JavaScript is dynamically typed, which allows for flexibility but can lead to unexpected runtime errors, TypeScript's static typing catches many of these errors during development. This helps developers identify and resolve issues early in the development process, leading to more robust and maintainable code.

Enhanced Code Quality

Static typing, combined with TypeScript's type inference system, promotes better code quality. TypeScript's compiler can catch type-related errors and provide meaningful feedback to developers, ensuring that variables, functions, and data structures are used correctly throughout the codebase. This results in fewer runtime errors and a more predictable codebase.

Improved Developer Productivity

TypeScript's strong tooling support and code editor integration, particularly in popular IDEs like Visual Studio Code, enhance developer productivity. Features such as auto-completion, intelligent code navigation, and real-time error checking help developers write code more efficiently and with fewer mistakes. This means less time spent debugging and more time building features.

Better Code Maintainability

TypeScript encourages the use of interfaces and type annotations, making codebases more self-documenting. This improves code maintainability by making it easier for developers to understand and work with the code. Additionally, TypeScript's static analysis can identify unused code and offer suggestions for code refactoring, leading to cleaner and more maintainable code.

Enhanced Collaboration

Collaboration is a critical aspect of modern software development. TypeScript can improve collaboration among developers by providing a clear contract for functions and data structures through types and interfaces. This makes it easier for teams to work together on large projects, as each team member can understand how different parts of the code interact.

Seamless Integration with JavaScript

Transitioning from JavaScript to TypeScript doesn't have to be an all-or-nothing decision. TypeScript is designed to be compatible with existing JavaScript codebases. Developers can gradually introduce TypeScript into their projects, allowing them to enjoy the benefits of static typing and enhanced tooling without the need for a complete rewrite.

Strong Community and Ecosystem

TypeScript has gained significant popularity in recent years, resulting in a thriving community and a growing ecosystem of libraries, tools, and resources. This means that developers can access a wealth of knowledge and support when working with TypeScript, making it easier to find solutions to common challenges and stay up-to-date with best practices.

Manual Migration

Install TypeScript

First, you'll need to install TypeScript. It's recommended to install it locally to ensure project-specific TypeScript versions don't conflict with each other. You can install TypeScript using npm or yarn:

npm install typescript --save-dev
# or
yarn add typescript --dev
Create a tsconfig.json File

Next, create a tsconfig.json file in the root of your project. This file contains configuration options for TypeScript. You can generate a basic tsconfig.json using the TypeScript CLI:

npx tsc --init
Install TypeScript Loader for Webpack

If you're using Webpack as your build system, you'll need to install the TypeScript loader:

npm install ts-loader --save-dev
# or
yarn add ts-loader --dev
Update Webpack Configuration

Modify your Webpack configuration to include TypeScript files and use the TypeScript loader. Here's an example of how you can update your webpack.config.js file:

const path = require('path');

module.exports = {
  // ... other webpack configuration options

  resolve: {
    // Add '.ts' to the list of extensions
    extensions: ['.ts', '.js'],

  module: {
    rules: [
        test: /\.ts$/, // Match TypeScript files
        exclude: /node_modules/,
        use: 'ts-loader',
      // ... other rules for your application

  // ... other webpack configuration options
Add IDE Plugins

Ensure that your development environment is set up to support TypeScript. Most modern code editors, like Visual Studio Code, offer excellent TypeScript support. Install the necessary TypeScript packages and plugins to enable features like code autocompletion, type checking, and automatic refactoring.

Convert Files One by One

One of the nice things about migrating a codebase from JavaScript to TypeScript is that you can do it incrementally, file by file. Applications can be a mix of JavaScript and TypeScript. We recommend starting with small leaf node components in your application, and slowly moving up the dependency tree until you reach page level files. As you might expect, the first step in converting a JavaScript file to TypeScript is to change the .js extension to .ts. If you are migrating a React codebase, you'll also need to convert .jsx files to .tsx. Since you have the TypeScript IDE plugin already installed, you'll see all of the TypeScript errors that need to be resolved in that file, and you'll need to fix each one. In general, most of the fixes will require creating new type definitions.

Best Practices

When using TypeScript, it's a good idea to make your code as clear as possible by specifying the types of your variables and functions. This helps catch mistakes early and makes your code easier to understand. Try not to use the "any" type too much because it can hide problems. Instead, create custom types to describe your data. If you need to work with different types of data, generics can be helpful. Also, keep an eye out for places where you can use union or intersection types to make your code more flexible. Remember to document your code well so that others (and future you) can understand it, and don't forget to test your types. Finally, stay up-to-date with TypeScript updates to take advantage of new features and improvements.

Automated Migration

For larger codebases, we recommend automating this process with a tool like Second. Connect Second to your GitHub account, run a module, and get a pull request! If you need additional help with this migration, whether you are doing it manually or automatically with Second, please connect with one of our migration experts on Discord.

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