Code splitting is an essential technique for optimizing web applications, especially for large-scale projects. It involves breaking up a large codebase into smaller chunks that can be loaded on-demand, reducing the initial load time and improving the user experience. In this tutorial, we'll explore how to implement code splitting with TypeScript and Webpack.


Prerequisites

Before we get started, you'll need to have the following installed on your machine:

  • Node.js and NPM (or Yarn)
  • TypeScript
  • Webpack


Step 1: Setting up the project

To get started, we'll create a new TypeScript project and install Webpack and its related dependencies. Run the following commands in your terminal:

mkdir my-project && cd my-project
npm init -y
npm install --save-dev typescript webpack webpack-cli ts-loader

We'll also create a new tsconfig.json file in the root of our project with the following configuration:

{
  "compilerOptions": {
    "target": "es5",
    "module": "esnext",
    "strict": true,
    "esModuleInterop": true,
    "sourceMap": true
  }
}

This tells TypeScript to transpile our code to ES5, use ES modules, enforce strict typing, enable interop with CommonJS modules, and generate source maps.


Step 2: Creating the entry point

Next, we'll create an entry point for our application in a new file called index.ts. This file will contain the code that kicks off our application and imports any necessary modules. Here's an example:

import { someFunction } from "./utils";

console.log("Hello from the entry point!");

someFunction();

We're importing a function called someFunction from a utils module, which we'll create next.


Step 3: Creating a utility module

Now, let's create a new TypeScript module called utils.ts in a new src directory. This module will contain a simple function that we'll use for testing code splitting. Here's the code:

export function someFunction() {
  console.log("This is a utility function.");
}


Step 4: Configuring Webpack

Now that we have our TypeScript files set up, let's create a new webpack.config.js file in the root of our project. This file will contain the configuration for our Webpack build. Here's an example:

const path = require("path");

module.exports = {
  entry: "./index.ts",
  output: {
    filename: "[name].[contenthash].js",
    path: path.resolve(__dirname, "dist"),
    clean: true,
  },
  module: {
    rules: [
      {
        test: /\.tsx?$/,
        use: "ts-loader",
        exclude: /node_modules/,
      },
    ],
  },
  resolve: {
    extensions: [".tsx", ".ts", ".js"],
  },
};

We're telling Webpack to use our index.ts file as the entry point, and to output a bundle file with a hashed name to the dist directory. We're also using the ts-loader plugin to transpile our TypeScript code. Finally, we're setting up some resolutions to enable TypeScript imports.


Step 5: Testing code splitting

Now that we have everything set up, let's test code splitting by splitting our utils module into a separate chunk. To do this, we'll modify our index.ts file to use dynamic imports instead of static imports. Here's the updated code:

console.log("Hello from the entry point!");

import("./utils").then((utils) => {
  utils.someFunction();
});

We're now importing the utils module dynamically using the import() function, which returns a Promise that resolves to the module object. We're then calling the someFunction function from the utils module.

To see the effect of code splitting, let's build and run our project. Run the following command in your terminal:

npm run build

This will compile and bundle our TypeScript code into the dist directory. Now, let's open the index.html file in a browser and check the console output. You should see the following:

Hello from the entry point!
This is a utility function.

This means that our code is working as expected, and that the utils module was loaded on-demand, separate from the main bundle.


Conclusion

In this tutorial, we explored how to implement code splitting with TypeScript and Webpack. We created a new TypeScript project, set up the TypeScript compiler and Webpack, created an entry point and a utility module, and configured Webpack to bundle our code and split it into chunks. We also tested code splitting by using dynamic imports to load our utility module on-demand. By using code splitting, we can optimize our web applications and improve the user experience.