How can I inspect disappearing element in a browser?

Extended solutions and explanations

Using breakpoints to pause DOM changes

When elements disappear upon interaction, like menus disappearing on a mouse click, leverage Chrome DevTools:

1. Open DevTools (F12 or Ctrl+Shift+I).
2. Navigate to the Sources feature.
3. On the right, locate the Event Listener Breakpoints.
4. Expand the Mouse category and tick the click checkbox (or relevant event).
5. Interact with your page to trigger the event—your script will pause.

This permits inspection of the DOM in the state it was in right before the element went away.

Keyboard shortcuts to the rescue

To freeze ephemeral elements, important keyboard shortcuts like F8 or Ctrl+/ come in handy. Deploy them while in DevTools to freeze the DOM, granting time for an inspection.

Faking page focus

From Chrome version 70 onwards, an option to emulate a focused page appears:

1. Hit Ctrl+Shift+P while in DevTools to open the command menu.
2. Type "focused" and pick the Emulate a focused page option.

This solution is beneficial for elements that only manifest when the window is in focus.

Breaking on DOM modifications

For easy DOM inspection, right-click the parent container (in either Firefox or Chrome), then choose Break on -> Subtree Modifications. Your browser will halt execution as the children start to change.

Exploring dynamic elements

For dynamic content, utilize Event breakpoints present in the Sources tab in Chrome or the innate DOM mutation features in Firefox. This approach offers great insight into complex element behavior.

Leveraging scope variables for inspection

Once paused at a breakpoint, dive deep into the Scope Variables section that materializes. Hidden here might be the variables and functions influencing the element's visibility.

Delaying the debugger for further inspection

When elements fade faster than a blink, embed a delayed debugger statement using setTimeout so there's ample time to inspect before disappearance.

setTimeout(() => { debugger; }, 500);  // Buy yourself an extra 500 ms for a latte before everything goes poof! 
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Proactive inspection strategies

Bookmarklets: Your debugging sidekick

If you're frequently debugging disappearing elements, craft a bookmarklet with the debugger code. That's one quick click to action when you smell trouble.

Select elements rapidly

When an element is playing hide and seek, use Ctrl+Shift+C (or Cmd+Shift+C on Mac) to swiftly select and inspect elements before they escape capture.

Capture the full life-cycle

Capture the full life-cycle of an element, from interaction to disappearance, with Event breakpoints like 'mousedown' or 'mouseover' in Chrome.

Solve mutation mysteries

Firefox's Break on DOM mutation feature can unravel dynamics of element disappearance. It's a mini detective novel, with you in the lead!