How do you detect a mobile browser without regexp?
Interviewer Expectations for this Question
01
Core Competency
Assesses fundamental understanding of JavaScript conventions, runtime behavior, and memory/performance considerations.
02
Evaluation Criteria
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
Comprehensive Model Answer
Verified Solution
You can detect mobile browsers by simply running through a list of devices and checking if the useragent matches anything. This is an alternative solution for RegExp usage,
function detectmob() {
if (
navigator.userAgent.match(/Android/i) ||
navigator.userAgent.match(/webOS/i) ||
navigator.userAgent.match(/iPhone/i) ||
navigator.userAgent.match(/iPad/i) ||
navigator.userAgent.match(/iPod/i) ||
navigator.userAgent.match(/BlackBerry/i) ||
navigator.userAgent.match(/Windows Phone/i)
) {
return true;
} else {
return false;
}
}
Candidate Response Strategy & Interview Tips
- Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
- Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
- Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.