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Updated: 2026年5月31日
Dom Event Delegation
Original task (JA): イベントデリゲーション
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Conclusion
Dom Event Delegation — free browser-based JavaScript (DOM) practice
Why it matters in real projects
親でリッスンして、e.targetで実際にクリックされた子を判定します。 Similar patterns appear daily in code review and production UI work.Step-by-step workflow
1. Read the guide and understand the goal of "Dom Event Delegation" 2. Review the JavaScript (DOM) editor pane and start from the starter code 3. Open hints if stuck; compare your diff with the sample solution 4. Click Run and inspect preview/console output 5. Auto-check looks for output containing: addEventListener, target, LI. 6. After success, continue with adjacent exercises in the same categoryCore concept explained
親でリッスンして、e.targetで実際にクリックされた子を判定します。Technical focus
Key JavaScript APIs: document.getElementById, console.log, addEventListener.Hint before you peek at the solution
e.targetでクリックされた要素を取得。tagNameでliか判定Sample solution walkthrough
JavaScript APIs used: document.getElementById, console.log, addEventListener. Verify spelling and async/await usage. Explanation: 親でリッスンして、e.targetで実際にクリックされた子を判定します。 Hint recap: e.targetでクリックされた要素を取得。tagNameでliか判定Solution code
📝 Sample code
document.getElementById('list')?.addEventListener('click', (e) => {
if (e.target?.tagName === 'LI') console.log(e.target.textContent);
});Common mistakes for this exact task
・Skipping the hint: e.targetでクリックされた要素を取得。tagNameでliか判定 ・getElementById returns null if the id string differs by even one characterTroubleshooting
Q: Preview does not change after Run A: Ensure you edited the JavaScript (DOM) pane and clicked Run. Q: Looks correct but check fails A: Auto-check looks for output containing: addEventListener, target, LI. Look for typos, full-width spaces, or unclosed tags. Q: Console shows errors A: Open DevTools Console and fix bracket/quote mismatches at the reported line. Q: Hard to type on mobile A: Use landscape mode or continue on desktop—the same URL keeps progress in localStorage.Interview / portfolio tips
・Explain the techniques in "Dom Event Delegation" in your own words within 30 seconds ・Practice walking through each line of the sample solution on a whiteboard ・Connect this task to a real component you would ship ・Mention responsive or accessibility trade-offs ・Describe when you use: document.getElementById, console.log, addEventListenerWhat to do after you pass
Move to the next exercise in the dom track, then continue the learning roadmap at /en/learning/js-basic/.Keywords
Free hands-on exercise covering イベントデリゲーション, dom, 中級, document.getElementById, console.log, addEventListener, dom event delegation—search-friendly guide for Dom Event Delegation.🧪 Try it here — safe to break things
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Jump to editor■ Exercise task
idが「list」の要素のクリックイベントをリッスンし、クリックされたliのtextContentをconsole.logで出力してください。
Hint if stuck
e.targetでクリックされた要素を取得。tagNameでliか判定