> ## Documentation Index
> Fetch the complete documentation index at: https://statsig-preview.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# How to run an AB Test in Node.js

> To run a simple A/B experiment in a webpage with Node.js using the Statsig SDK, you'll go through a few essential steps. This will involve setting up a simple Node.js server, integrating with the Statsig SDK for A/B testing, and configuring your experiment in the Statsig console.

### Step 1: Set Up a Basic Node.js Server

1. **Initialize Your Node.js Project**:
   * Create a new directory for your project, navigate into it, and run `npm init -y` to create a `package.json` file.
2. **Install Necessary Packages**:
   * Install Express for your web server and the Statsig SDK for Node.js by running:
   ```Bash theme={null}
   npm install express statsig-node
   ```
3. **Create Your Server**:
   * Create an `index.js` file and set up a basic Express server. Here's a simple example:
   ```js theme={null}
   const express = require('express');
   const app = express();
   const port = 3000;
   app.get('/', (req, res) => {
       res.send('Hello, World!');
   });
   app.listen(port, () => {
       console.log(`Server listening at http://localhost:${port}`);
   });
   ```
   * Verify the app runs by issuing `node index.js` command

### Step 2: Integrate Statsig for A/B Testing

1. **Initialize Statsig**:
   * At the top of your `index.js`, require the Statsig SDK and initialize it with your server-side SDK key.
   * Modify your route to serve different content based on the experiment's variant.
   * Ensure you replace `'your-server-sdk-key'` with your actual Statsig server-side SDK key and `'your_experiment_key'` with the name of your experiment.
   ```js theme={null}
   const statsig = require('statsig-node');
   const express = require('express');
   const app = express();
   const port = 3000;
   // Initialize Statsig server-side SDK
   statsig.initialize('your-server-sdk-key').then(() => {
     app.get('/', async (req, res) => {
       const user = { userID: 'user123' }; // Customize as needed
       const experiment = statsig.getExperimentSync(user, 'experiment_name');
       const ev = experiment.getValue('parameter_name', 'Default Text');
       res.send(`<h1>${ev}</h1>`);
     });
   });
   app.listen(port, () => {
     console.log(`Server listening at http://localhost:${port}`);
   });
   ```
   * Run the app by issuing `node index.js` command

### Step 3: Create Your A/B Test in Statsig Console

1. **Log into Statsig Console**:
   * Go to the Statsig Console and log in.
2. **Create a New Experiment**:
   * Navigate to the "Experiments" section and click on "Create New".
   * Fill in the details for your experiment, including giving it a unique key (e.g., `'your_experiment_key'`).
3. **Configure Experiment Variants**:
   * Add variants for your experiment (e.g., `control` and `test`).
   * Within each variant's configuration, add a parameter named `textToShow` and assign the text you wish to display for each variant.
     <Frame>
       <img src="https://mintcdn.com/statsig-preview/WoeZk8QBCrPBwbAK/images/310288589-8a667aeb-9189-4e7d-8a22-a42dabcdfe09(1).png?fit=max&auto=format&n=WoeZk8QBCrPBwbAK&q=85&s=5685bc10fb533df8c2fb2f94861b386f" width="1131" height="870" data-path="images/310288589-8a667aeb-9189-4e7d-8a22-a42dabcdfe09(1).png" />
     </Frame>
4. **Launch the Experiment**:
   * After setting up your variants and parameters, save and start the experiment.

By following these steps, you've created a simple Node.js application that runs an A/B test to serve different text content based on the variant assigned to a user in the Statsig experiment. This setup enables you to conduct A/B testing efficiently, allowing you to make data-driven decisions based on user interaction with your application.