🌐 Frontend & Web

JavaScript's substring(): Quirky, Useful, Utterly Confusing

JavaScript's substring() looks innocent. It bites with swapped args and NaN forgiveness—tripping even vets.

DevTools Feed Apr 03, 2026 3 min read
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Diagram showing JavaScript string indices and substring extraction ranges

⚡ Key Takeaways

  • substring() auto-swaps args and forgives NaN/negatives—handy but hides bugs. 𝕏
  • Prefer slice() for negatives and predictability; substring for legacy tolerance. 𝕏
  • Always validate indices; JS strings butcher UTF-8 emojis without care. 𝕏
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#javascript #slice vs substring #string methods #substring method

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Originally reported by dev.to

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