As software developers, it is crucial to ensure a smooth and controlled release of new features in our applications. One way to achieve this is by using feature flags, which allow us to toggle the availability of a feature in real-time without the need for a complete code deployment.

In this blog post, we will learn how to implement feature flags in a Rollup.js project to control the release of new application features. Let’s get started!

What are feature flags?

Feature flags, also known as feature toggles, are a technique used in software development to enable or disable features in an application. By using feature flags, developers can separate feature release from code deployment, giving them better control over the release process.

Setting up a Rollup.js project

Before we can implement feature flags in our Rollup.js project, we need to set up a basic project structure. Assuming you have Node.js and npm installed, follow these steps:

1. Create a new directory for your project: mkdir rollup-feature-flags
2. Navigate to the project directory: cd rollup-feature-flags
3. Initialize a new npm project: npm init -y
4. Install Rollup.js as a development dependency: npm install --save-dev rollup

Once the basic project structure is set up with Rollup.js, we can proceed to implement feature flags.

Implementing feature flags

1. Create a new file called featureFlags.js in the project directory.
2. In featureFlags.js, we will define our feature flags as variables or constants. For example, let’s create a feature flag for a new payment gateway:

export const ENABLE_PAYMENT_GATEWAY = true;

1. In your main JavaScript file (e.g., app.js), import the feature flag(s) defined in featureFlags.js:

import { ENABLE_PAYMENT_GATEWAY } from './featureFlags.js';

if (ENABLE_PAYMENT_GATEWAY) {
  // Enable code for the new payment gateway feature
  // ...
} else {
  // Feature is disabled, handle accordingly
  // ...
}

1. To bundle the code using Rollup.js, create a rollup.config.js file in the project directory:

import { terser } from 'rollup-plugin-terser';

export default {
  input: 'app.js',
  output: {
    file: 'bundle.js',
    format: 'iife',
    plugins: [terser()]
  }
};

1. Run the Rollup.js build command to generate the bundled file:

npx rollup -c

Now, whenever you want to release the new payment gateway feature, simply change the value of ENABLE_PAYMENT_GATEWAY in featureFlags.js to true. Similarly, set it to false to disable the feature.

Conclusion

By implementing feature flags in your Rollup.js projects, you can have better control over the release of new application features. This allows you to gradually enable or disable features without the need for a complete code deployment. Rollup.js, with its powerful module bundling capabilities, helps streamline the build process and make the feature toggle implementation seamless.

#RollupJS #FeatureFlags