Event Bubbling vs Event Capturing in JavaScript

When you click on an element inside nested elements, the event doesn’t just happen on that element — it travels through the DOM. There are two ways this can happen: capturing and bubbling.

1. Event Capturing (trickle down)

• The event starts at the top (document) and goes down through each parent until it reaches the target.
• Analogy: a grandparent tells a message → parent → child.

2. Event Bubbling (bubble up)

• The event starts at the target element and then goes up through the parents until the root (document).
• Analogy: bubbles rise from the bottom of a glass to the top.

3. Default in JavaScript

• By default, JavaScript uses bubbling.
• To use capturing, pass true as the third parameter in addEventListener.

// Bubbling (default)
button.addEventListener("click", () => {
  console.log("Button clicked!");
});

// Capturing
div.addEventListener(
  "click",
  () => {
    console.log("DIV clicked during capturing!");
  },
  true // 👈 capturing enabled
);

4. Event Flow Order

When you click the button:

1. Capturing phase: document → body → div → button
2. Target phase: the button itself
3. Bubbling phase: button → div → body → document

5. Why does this matter?

• Capturing: less common, useful if you want to intercept early.
• Bubbling: very common, great for event delegation (attach one listener to a parent instead of every child).

🧠 Quick Mental Model

• Capturing = trickle down (parent → child)
• Bubbling = bubble up (child → parent)

⚡ That’s it! Now you know how events travel in JavaScript.