javascript 16 lines · 7 steps

Auto-resizing a textarea to fit its content

A textarea grows with its text by measuring scrollHeight on every input and setting its own height.

Explained by highlit

Intermediate dom event-listener cleanup closures layout

1function autoResizeTextarea(textarea, { maxHeight = Infinity } = {}) {
const resize = () => {
  textarea.style.height = 'auto';
  const contentHeight = textarea.scrollHeight;
  const nextHeight = Math.min(contentHeight, maxHeight);
  textarea.style.height = `${nextHeight}px`;
  textarea.style.overflowY = contentHeight > maxHeight ? 'auto' : 'hidden';
};
9 
textarea.style.resize = 'none';
textarea.style.boxSizing = 'border-box';
textarea.addEventListener('input', resize);
resize();
14 
return () => textarea.removeEventListener('input', resize);
16}

01 / 01

STEP 01

Walkthrough

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Three takeaways

1Resetting height to 'auto' before reading scrollHeight is what lets a textarea shrink as well as grow.
2Clamping with Math.min and toggling overflowY gives you a scrollbar only once a max height is reached.
3Returning a teardown function makes the listener easy to remove and prevents leaks.

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