Why JavaScript String Length Lies to You

📰 Dev.to · Tiago

Learn why JavaScript's string length can be misleading and how to handle Unicode characters correctly

intermediate Published 18 Feb 2026
Action Steps
  1. Understand the difference between code points, code units, and grapheme clusters in Unicode
  2. Use the correct methods to calculate string length, such as iterating over grapheme clusters
  3. Avoid naive string truncation that can corrupt text, especially when dealing with non-ASCII characters
  4. Use libraries like grapheme-js to handle grapheme clusters correctly
  5. Test your code with diverse text inputs to ensure correctness
Who Needs to Know This

Developers working with text processing and internationalization can benefit from understanding the nuances of JavaScript's string length, as it can impact the correctness of their code

Key Insight

💡 JavaScript's string length does not always reflect the actual number of visible characters, due to the complexities of Unicode

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🚨 JavaScript's string length can lie to you! 🚨 Learn about code points, code units, and grapheme clusters to handle Unicode correctly

Full Article

Understanding code points, code units, and grapheme clusters — and why naive string truncation can corrupt your text.
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