📞 Callbacks Explained Like You're 5

Leave your number, I'll call you back

Day 51 of 149

👉 Full deep-dive with code examples

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The Phone Call

You call a busy restaurant for a reservation.

Bad: "Please hold..." (wait on the line for 30 min) 😫

Better: "Leave your number, we'll call you back when ready!"

You hang up, do other things. They call when ready!

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In Code

// "Call me back when you're done"
fetchData(function (result) {
  console.log("Got the data!", result);
});

// Meanwhile, do other things!
console.log("I'm not waiting!");

Output:

I'm not waiting!
Got the data! {...}

The callback runs WHEN the data arrives, not before!

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Why Callbacks?

JavaScript can't wait! If it paused for every slow thing:

• Fetching data: a couple of seconds... frozen
• Loading images: a few seconds... frozen
• User can't click anything! 😤

Callbacks: "Keep going, I'll handle it when ready."

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The Problem: Callback Hell

Nested callbacks get ugly:

getData(function (a) {
  getMore(a, function (b) {
    getEvenMore(b, function (c) {
      // Help! 🆘
    });
  });
});

This is why Promises were invented!

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In One Sentence

Callbacks are functions you pass to be called later when an operation completes, instead of waiting.

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