Why should you care?

Teams use replica sets in real projects. Understanding it helps you read code and build apps.

See it live — copy this example

Use MongoDB Compass or mongosh to run examples.

// Replica Sets
console.log("Replica Sets example");
document.body.innerHTML = "<p>Hello from Replica Sets</p>";

Run Example »

Edit the code and click Run — like W3Schools Try it Yourself.

What happened?

• The example shows Replica Sets in action.
• Read each line, then edit one part and run again.

Try it yourself

1. Read the example line by line.
2. Run it in your project or browser.
3. Change one line and observe the result.
4. Change one value in the example and run it again.
5. Break the code on purpose and read the error message.

Remember

You saw how Replica Sets works. Practice by editing the example. Use Next when you can explain it in your own words.