“JavaScript Insertar texto en TextARea en la posición del cursor” Código de respuesta

JavaScript Insertar texto en TextARea en la posición del cursor

function insertAtCaret(areaId, text) {
  var txtarea = document.getElementById(areaId);
  var strPos = 0;
  var br = ((txtarea.selectionStart || txtarea.selectionStart == '0') ?
            "ff" : (document.selection ? "ie" : false));
  if (br == "ie") {
    txtarea.focus();
    var range = document.selection.createRange();
    range.moveStart('character', -txtarea.value.length);
    strPos = range.text.length;
  } else if (br == "ff") strPos = txtarea.selectionStart;

  var front = (txtarea.value).substring(0, strPos);
  var back = (txtarea.value).substring(strPos, txtarea.value.length);
  txtarea.value = front + text + back;
  strPos = strPos + text.length;
  if (br == "ie") {
    txtarea.focus();
    var range = document.selection.createRange();
    range.moveStart('character', -txtarea.value.length);
    range.moveStart('character', strPos);
    range.moveEnd('character', 0);
    range.select();
  } else if (br == "ff") {
    txtarea.selectionStart = strPos;
    txtarea.selectionEnd = strPos;
    txtarea.focus();
  }
}