How to Use GitHub Copilot to Write a Function in 15 Minutes

Imagine you’re a solo founder with a million things on your plate, and coding isn’t your strongest suit. You need to write a function, but the thought of diving into documentation and syntax is daunting. Enter GitHub Copilot, your AI-powered coding assistant that can help you whip up code in a fraction of the time. In this guide, I’ll show you how to use GitHub Copilot to write a function in just 15 minutes.

Prerequisites

Before we dive in, here are the tools and accounts you need:

• GitHub Account: Sign up for free at GitHub.
• Visual Studio Code (VS Code): Download and install from VS Code.
• GitHub Copilot: You’ll need a subscription to GitHub Copilot. Pricing is currently $10/month or $100/year (as of July 2026).

Step-by-Step Guide

Step 1: Set Up Your Environment (5 minutes)

1. Install Visual Studio Code: Make sure you have VS Code installed. If you haven't already, download it and set it up.

2. Install GitHub Copilot: Open VS Code, go to the Extensions (Ctrl+Shift+X), and search for "GitHub Copilot". Click "Install".

3. Sign In: After installation, sign in to your GitHub account to activate Copilot.

Step 2: Create a New File (2 minutes)

1. Create a New File: In VS Code, create a new file and name it function.js (or any extension depending on your programming language).

2. Write a Comment: Start by writing a comment that describes the function you want to create. For example, // Function to calculate the factorial of a number.

Step 3: Let Copilot Work Its Magic (5 minutes)

1. Invoke Copilot: Start typing the function definition. For example:

   function factorial(n) {
   

   As you type, GitHub Copilot will suggest completions. Use the Tab key to accept a suggestion.

2. Review the Code: Once Copilot provides a full implementation, review the code. Make sure it fits your requirements. Here’s an example output:

   function factorial(n) {
       if (n < 0) return undefined;
       if (n === 0) return 1;
       return n * factorial(n - 1);
   }
   

Step 4: Test Your Function (2 minutes)

1. Write Test Cases: Below your function, add some test cases to see if it works as expected.

   console.log(factorial(5)); // 120
   console.log(factorial(0)); // 1
   console.log(factorial(-1)); // undefined
   

2. Run Your Code: Use Node.js or your preferred runtime to execute the code and verify the output.

Step 5: Troubleshooting (1 minute)

If Copilot doesn’t generate the desired code, try modifying your comment or adding more detail. For example, instead of just saying “Function to calculate the factorial,” you could say “Function to calculate the factorial of a non-negative integer.”

What Could Go Wrong

• Inaccurate Suggestions: Sometimes Copilot might suggest incorrect or insecure code. Always review and test the output.
• Limited Context Understanding: If your comment is vague, Copilot might not generate relevant code. Be as specific as possible.

What’s Next

Now that you’ve successfully written a function using GitHub Copilot, consider exploring more complex functions or integrating Copilot into larger projects. You can also check out the Built This Week podcast for more tips on using AI tools effectively in your workflow.

Conclusion

Using GitHub Copilot can significantly speed up your coding process, especially when you need to write functions quickly. In just 15 minutes, you can leverage AI to create functional code that meets your needs.

If you’re just starting out, I recommend focusing on simple functions first and gradually increasing complexity as you get comfortable with the tool.