function getCaretCharacterOffsetWithin(element) {
  var caretOffset = 0;
  var doc = element.ownerDocument || element.document;
  var win = doc.defaultView || doc.parentWindow;
  var sel;
  if (typeof win.getSelection != "undefined") {
    sel = win.getSelection();
    if (sel.rangeCount > 0) {
      var range = win.getSelection().getRangeAt(0);
      var preCaretRange = range.cloneRange();
      preCaretRange.selectNodeContents(element);
      preCaretRange.setEnd(range.endContainer, range.endOffset);
      caretOffset = preCaretRange.toString().length;
    }
  } else if ((sel = doc.selection) && sel.type != "Control") {
    var textRange = sel.createRange();
    var preCaretTextRange = doc.body.createTextRange();
    preCaretTextRange.moveToElementText(element);
    preCaretTextRange.setEndPoint("EndToEnd", textRange);
    caretOffset = preCaretTextRange.text.length;
  }
  return caretOffset;
}

function getCaretPosition() {
  if (window.getSelection && window.getSelection().getRangeAt) {
    var range = window.getSelection().getRangeAt(0);
    var selectedObj = window.getSelection();
    var rangeCount = 0;
    var childNodes = selectedObj.anchorNode.parentNode.childNodes;
    for (var i = 0; i < childNodes.length; i++) {
      if (childNodes[i] == selectedObj.anchorNode) {
        break;
      }
      if (childNodes[i].outerHTML)
        rangeCount += childNodes[i].outerHTML.length;
      else if (childNodes[i].nodeType == 3) {
        rangeCount += childNodes[i].textContent.length;
      }
    }
    return range.startOffset + rangeCount;
  }
  return -1;
}

獲取光標(biāo)坐標(biāo)

function getCaretCoordinates() {
  let x = 0,
    y = 0;
  const isSupported = typeof window.getSelection !== "undefined";
  if (isSupported) {
    const selection = window.getSelection();
    if (selection.rangeCount !== 0) {
      const range = selection.getRangeAt(0).cloneRange();
      range.collapse(true);
      const rect = range.getClientRects()[0];
      if (rect) {
        x = rect.left;
        y = rect.top;
      }
    }
  }
  return { x, y };
}