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Updated: 2026年5月31日
Project Filter
Original task (JA): フィルター
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Conclusion
Project Filter — free browser-based JavaScript practice
Why it matters in real projects
filterで条件に合う要素だけの配列を作れます。 Similar patterns appear daily in code review and production UI work.Step-by-step workflow
1. Read the guide and understand the goal of "Project Filter" 2. Review the JavaScript 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: 3, 4, 5. 6. After success, continue with adjacent exercises in the same categoryCore concept explained
filterで条件に合う要素だけの配列を作れます。Technical focus
Key JavaScript APIs: console.log, .filter(.Hint before you peek at the solution
arr.filter(n => n >= 3)Sample solution walkthrough
JavaScript APIs used: console.log, .filter(. Verify spelling and async/await usage. Explanation: filterで条件に合う要素だけの配列を作れます。 Hint recap: arr.filter(n => n >= 3)Solution code
📝 Sample code
const arr = [1, 2, 3, 4, 5];
const filtered = arr.filter(n => n >= 3);
console.log(filtered);Common mistakes for this exact task
・Skipping the hint: arr.filter(n => n >= 3)Troubleshooting
Q: Preview does not change after Run A: Ensure you edited the JavaScript pane and clicked Run. Q: Looks correct but check fails A: Auto-check looks for output containing: 3, 4, 5. 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 "Project Filter" 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: console.log, .filter(What to do after you pass
Move to the next exercise in the project track, then continue the learning roadmap at /en/learning/project/.Keywords
Free hands-on exercise covering フィルター, project, 上級, console.log, .filter(, project filter—search-friendly guide for Project Filter.🧪 Try it here — safe to break things
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Jump to editor■ Exercise task
配列[1,2,3,4,5]から3以上の数だけをfilterで抽出し、console.logで出力してください。
Hint if stuck
arr.filter(n => n >= 3)