The answer
Clamp the value: percent = Math.max(0, Math.min(100, percent)). This ensures the progress bar never overflows or goes negative. Always clamp before setting the width.
Progress Bar Interview Questions
How do you handle progress values above 100% or below 0%?
More FAQs in Progress Bar Interview Questions
Use setInterval to increment progress: const interval = setInterval(() => { progress += 1; bar.style.width = progress + '%'; if (progress >= 100) clearInterval(interval); }, 50). Use CSS transition for smooth animation.
Use XMLHttpRequest (not fetch). Listen for xhr.upload 'progress' event: if (e.lengthComputable) { const percent = (e.loaded / e.total) * 100; setProgress(percent); }. fetch does not support upload progress events.
Add role='progressbar', aria-valuenow (current value), aria-valuemin='0', aria-valuemax='100'. Use aria-live='polite' to announce changes for screen readers. This makes the progress bar usable with assistive technology.
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