Auto-growing Textarea of ShadCN

textarea.tsx

import * as React from "react";
import { cn } from "@/lib/utils";

const Textarea = React.forwardRef<
  HTMLTextAreaElement,
  React.ComponentProps<"textarea">
>(({ className, ...props }, ref) => {
  const textareaRef = React.useRef<HTMLTextAreaElement | null>(null);

  const calculateHeight = React.useCallback(() => {
    const textarea = textareaRef.current;
    if (!textarea) return;

    // Store the current scroll position
    const scrollPos = textarea.scrollTop;

    // Reset height to auto to get the correct scrollHeight
    textarea.style.height = "auto";

    // Get the scroll height and add a small padding
    const scrollHeight = textarea.scrollHeight;

    // Set the new height
    textarea.style.height = `${scrollHeight}px`;

    // Restore the scroll position
    textarea.scrollTop = scrollPos;
  }, []);

  React.useEffect(() => {
    calculateHeight();
    // Add resize observer to handle window/container resizing
    const resizeObserver = new ResizeObserver(calculateHeight);
    if (textareaRef.current) {
      resizeObserver.observe(textareaRef.current);
    }

    return () => resizeObserver.disconnect();
  }, [calculateHeight, props.value]);

  const handleInput = (e: React.ChangeEvent<HTMLTextAreaElement>) => {
    calculateHeight();
    if (props.onChange) {
      props.onChange(e);
    }
  };

  return (
    <textarea
      className={cn(
        "flex min-h-[60px] w-full rounded-md border border-input bg-transparent px-3 py-2 text-base shadow-sm placeholder:text-muted-foreground focus-visible:outline-none focus-visible:ring-1 focus-visible:ring-ring disabled:cursor-not-allowed disabled:opacity-50 md:text-sm",
        "text-xs transition-all duration-100 md:text-sm",
        className,
        "overflow-y-hidden",
      )}
      ref={(element) => {
        // Handle both forwardRef and internal ref
        textareaRef.current = element;
        if (typeof ref === "function") {
          ref(element);
        } else if (ref) {
          ref.current = element;
        }
      }}
      onChange={handleInput}
      {...props}
    />
  );
});

Textarea.displayName = "Textarea";

export { Textarea };