As web development has evolved, browsers have introduced new features and APIs to make the web more interactive and user-friendly. However, not all browsers support these features and APIs, leaving developers to rely on polyfills to ensure their projects work across all platforms. In this article, we will discuss how to add polyfills to your project to ensure your code works as intended.

What are Polyfills?

Polyfills are JavaScript code that replicate browser APIs that are not natively available on certain browsers. By using polyfills, developers can use modern JavaScript features and APIs that may not be supported by all browsers without having to worry about compatibility issues.

Polyfills can be implemented in various ways, including as standalone scripts or through module bundlers like Webpack or Rollup. In this article, we will focus on using polyfills through Webpack.

Adding Polyfills with Webpack

Webpack is a popular module bundler used by many developers. It has a built-in feature that allows for the addition of polyfills through the @babel/preset-env package.

Here are the steps to add polyfills to your project using Webpack:

1. Install @babel/preset-env and core-js

First, you will need to install the @babel/preset-env package and the core-js package, which provides the polyfills for the targeted browsers. You can install both packages using npm or yarn by running the following command:

npm install --save-dev @babel/preset-env core-js

// or 

yarn add --dev @babel/preset-env core-js

2. Configure @babel/preset-env

Next, you will need to configure @babel/preset-env in your Webpack configuration file (webpack.config.js). You can do this by adding the following code:

module.exports = {
  // ... other configurations
  module: {
    rules: [
      {
        test: /\.m?js$/,
        exclude: /(node_modules|bower_components)/,
        use: {
          loader: 'babel-loader',
          options: {
            presets: [
              [
                '@babel/preset-env',
                {
                  useBuiltIns: 'usage',
                  corejs: {
                    version: 3,
                    proposals: true
                  },
                  targets: {
                    chrome: '58',
                    ie: '11'
                  }
                }
              ]
            ]
          }
        }
      }
    ]
  }
}

In the code above, we are using the useBuiltIns option set to usage, which instructs @babel/preset-env to automatically include polyfills based on the used features in your code. We also specify the corejs version as 3 and proposals set to true, which includes polyfills for experimental features.

Finally, we specify the targeted browsers through the targets option. In this example, we are targeting Chrome version 58 and Internet Explorer version 11.

3. Verify the Polyfills

You can verify that the polyfills are correctly included in your code by running the following command in your terminal:

npx webpack --mode production

This will generate a dist folder containing the bundled code. Open the dist folder and locate the main.js file. You will see that the polyfills are included at the beginning of the file.

Conclusion

In this article, we discussed how to add polyfills to your project using Webpack. By including polyfills, you can ensure that your code works across all browsers without having to worry about compatibility issues.

Polyfills are a powerful tool for modern web development and can greatly enhance the user experience of a web application. In this article, we'll explore what polyfills are and how they can be added to a project to improve cross-browser compatibility.