Inserting a text where cursor is using Javascript/jquery

Question

Use this, from here:

function insertAtCaret(areaId, text) {
  var txtarea = document.getElementById(areaId);
  if (!txtarea) {
    return;
  }

  var scrollPos = txtarea.scrollTop;
  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 ieRange = document.selection.createRange();
    ieRange.moveStart('character', -txtarea.value.length);
    ieRange.moveStart('character', strPos);
    ieRange.moveEnd('character', 0);
    ieRange.select();
  } else if (br == "ff") {
    txtarea.selectionStart = strPos;
    txtarea.selectionEnd = strPos;
    txtarea.focus();
  }

  txtarea.scrollTop = scrollPos;
}

<textarea id="textareaid"></textarea>
<a href="#" onclick="insertAtCaret('textareaid', 'text to insert');return false;">Click Here to Insert</a>

Maybe a shorter version, would be easier to understand?

    jQuery("#btn").on('click', function() {
        var $txt = jQuery("#txt");
        var caretPos = $txt[0].selectionStart;
        var textAreaTxt = $txt.val();
        var txtToAdd = "stuff";
        $txt.val(textAreaTxt.substring(0, caretPos) + txtToAdd + textAreaTxt.substring(caretPos) );
    });

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>

<textarea id="txt" rows="15" cols="70">There is some text here.</textarea>
<input type="button" id="btn" value="OK" />

I wrote this in response to How to add a text to a textbox from the current position of the pointer with jquery?

The approved answer from George Claghorn worked great for simply inserting text at the cursor position. If the user had selected text though, and you want that text to be replaced (the default experience with most text), you need to make a small change when setting the 'back' variable.

Also, if you don't need to support older versions of IE, modern versions support textarea.selectionStart, so you can take out all of the browser detection, and IE-specific code.

Here is a simplified version that works for Chrome and IE11 at least, and handles replacing selected text.

function insertAtCaret(areaId, text) {
    var txtarea = document.getElementById(areaId);
    var scrollPos = txtarea.scrollTop;
    var caretPos = txtarea.selectionStart;

    var front = (txtarea.value).substring(0, caretPos);
    var back = (txtarea.value).substring(txtarea.selectionEnd, txtarea.value.length);
    txtarea.value = front + text + back;
    caretPos = caretPos + text.length;
    txtarea.selectionStart = caretPos;
    txtarea.selectionEnd = caretPos;
    txtarea.focus();
    txtarea.scrollTop = scrollPos;
}

The code above didn't work for me in IE. Here's some code based on this answer.

I took out the getElementById so I could reference the element in a different way.

function insertAtCaret(element, text) {
  if (document.selection) {
    element.focus();
    var sel = document.selection.createRange();
    sel.text = text;
    element.focus();
  } else if (element.selectionStart || element.selectionStart === 0) {
    var startPos = element.selectionStart;
    var endPos = element.selectionEnd;
    var scrollTop = element.scrollTop;
    element.value = element.value.substring(0, startPos) +
      text + element.value.substring(endPos, element.value.length);
    element.focus();
    element.selectionStart = startPos + text.length;
    element.selectionEnd = startPos + text.length;
    element.scrollTop = scrollTop;
  } else {
    element.value += text;
    element.focus();
  }
}

input{width:100px}
label{display:block;margin:10px 0}

<label for="in2copy">Copy text from: <input id="in2copy" type="text" value="x"></label>
<label for="in2ins">Element to insert: <input id="in2ins" type="text" value="1,2,3" autofocus></label>
<button onclick="insertAtCaret(document.getElementById('in2ins'),document.getElementById('in2copy').value)">Insert</button>

EDIT: Added a running snippet, jQuery is not being used.