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Updated: 2026年5月31日
If Statement
Original task (JA): if文
📌
Conclusion
If Statement — free browser-based JavaScript practice
Why it matters in real projects
ifで条件分岐。比較演算子は >=, <, === など。 Similar patterns appear daily in code review and production UI work.Step-by-step workflow
1. Read the guide and understand the goal of "If Statement" 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: 成人. 6. After success, continue with adjacent exercises in the same categoryCore concept explained
ifで条件分岐。比較演算子は >=, <, === など。Technical focus
Key JavaScript APIs: console.log.Hint before you peek at the solution
if (age >= 18) { ... } else { ... }Sample solution walkthrough
JavaScript APIs used: console.log. Verify spelling and async/await usage. Explanation: ifで条件分岐。比較演算子は >=, <, === など。 Hint recap: if (age >= 18) { ... } else { ... }Solution code
📝 Sample code
const age = 20;
if (age >= 18) {
console.log('成人');
} else {
console.log('未成年');
}Common mistakes for this exact task
・Skipping the hint: if (age >= 18) { ... } else { ... }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: 成人. 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 "If Statement" 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.logWhat to do after you pass
Move to the next exercise in the js-basic track, then continue the learning roadmap at /en/learning/js-basic/.Keywords
Free hands-on exercise covering if文, js-basic, 入門, console.log, if statement—search-friendly guide for If Statement.🧪 Try it here — safe to break things
Use the editor below to write code and preview instantly.
Jump to editor■ Exercise task
ageが18以上のとき「成人」、未満のとき「未成年」をconsole.logで出力してください。ageは20。
Hint if stuck
if (age >= 18) { ... } else { ... }