如何在textarea中获得光标位置？

function getCursorPosition(textarea) {
  if (textarea.selectionStart) {
    return textarea.selectionStart;
  } else if (document.selection) {
    textarea.focus();
    var selection = document.selection.createRange();
    var length = document.selection.createRange().text.length;
    selection.moveStart('character', -textarea.value.length);
    return selection.text.length - length;
  }
}

function getCursorPosition(textarea) {
  var startPos = textarea.prop('selectionStart');
  var endPos = textarea.prop('selectionEnd');
  return startPos;
}

 <textarea ref="textarea" @input="getCursorPosition"></textarea>
</template><script>
export default {
  methods: {
    getCursorPosition() {
      const textarea = this.$refs.textarea;
      const startPos = textarea.selectionStart;
      const endPos = textarea.selectionEnd;
      return startPos;
    },
  },
};
</script>

import React, { useRef } from 'react';

function Textarea() {
  const textareaRef = useRef(null);

  const getCursorPosition = () => {
    const textarea = textareaRef.current;
    const startPos = textarea.selectionStart;
    const endPos = textarea.selectionEnd;
    return startPos;
  };

  return<textarea ref={textareaRef} onInput={getCursorPosition} />;
}

export default Textarea;