How To Find INPUT And TEXTAREA Caret Position Coordinates Using JavaScript?

Question

Me trying to find out caret position coordinates with respect to document(Whole Web Page) in a TextArea or Input of type="text" on JavaScript HTML DOM Events functions like onkeydown, onkeypress, onkeyup etc...

For this I created the below HTML...

<input dir="rtl" type="text" id="TEST_INPUT" onkeydown="myFunction(this)"></input>
<textarea dir="rtl" id="TEST_TEXTAREA" onkeyup="myFunction(this)"></textarea>

And running the below JavaScript...

<script type="text/javascript">
/* Main Function
----------------------------------------------- */
function myFunction(Desired_ID){
    // Extra Codes Here ETC...
    document.getElementById(Desired_ID.id).style.backgroundColor = "red";
    // Extra Codes Here ETC...
    var coords = getSelectionCoords(Desired_ID);
    alert(coords.left + ", " + coords.top);
    // Extra Codes Here ETC...
}

/* Get Caret XY Coordinate
----------------------------------------------- */
function getSelectionCoords(Desired_ELEMENT) {
// ------>>> What To Do Here Is The Problem To Cover All Browsers <<<------
return {left:x,top:y};
}
</script>

I searched in StackOverflow and found many one but everyone have some sort of problems while using or running that are shared below...

• http://jsfiddle.net/dandv/aFPA7/
• http://jsfiddle.net/mLocgoeq/
• http://jsfiddle.net/NFJ9r/132/

Where mine working DEMO is at https://jsfiddle.net/qjkkqdg2/ on which I am working out so can your share any tip or idea to go through it...???

Answer 1

After keep working and trying, I found my desired answer and here I am sharing it below in the form of code that you can see at https://jsfiddle.net/qjkkqdg2/1/ also...

<script type="text/javascript">
/* Main Function
----------------------------------------------- */
function myFunction(Desired_ID){
    // Extra Codes Here ETC...
    document.getElementById(Desired_ID.id).style.backgroundColor = "red";
    // Extra Codes Here ETC...
    var coordinates = getCaretCoordinates(Desired_ID, Desired_ID.selectionStart);
    alert(coordinates.left + ", " + coordinates.top);
    // Extra Codes Here ETC...
}

/* Get Caret XY Coordinate
----------------------------------------------- */
/* jshint browser: true */
(function () {

// The properties that we copy into a mirrored div.
// Note that some browsers, such as Firefox,
// do not concatenate properties, i.e. padding-top, bottom etc. -> padding,
// so we have to do every single property specifically.
var properties = [
  'direction',  // RTL support
  'boxSizing',
  'width',  // on Chrome and IE, exclude the scrollbar, so the mirror div wraps exactly as the textarea does
  'height',
  'overflowX',
  'overflowY',  // copy the scrollbar for IE

  'borderTopWidth',
  'borderRightWidth',
  'borderBottomWidth',
  'borderLeftWidth',
  'borderStyle',

  'paddingTop',
  'paddingRight',
  'paddingBottom',
  'paddingLeft',

  // https://developer.mozilla.org/en-US/docs/Web/CSS/font
  'fontStyle',
  'fontVariant',
  'fontWeight',
  'fontStretch',
  'fontSize',
  'fontSizeAdjust',
  'lineHeight',
  'fontFamily',

  'textAlign',
  'textTransform',
  'textIndent',
  'textDecoration',  // might not make a difference, but better be safe

  'letterSpacing',
  'wordSpacing',

  'tabSize',
  'MozTabSize'

];

var isBrowser = (typeof window !== 'undefined');
var isFirefox = (isBrowser && window.mozInnerScreenX != null);

function getCaretCoordinates(element, position, options) {
  if(!isBrowser) {
    throw new Error('textarea-caret-position#getCaretCoordinates should only be called in a browser');
  }

  var debug = options && options.debug || false;
  if (debug) {
    var el = document.querySelector('#input-textarea-caret-position-mirror-div');
    if ( el ) { el.parentNode.removeChild(el); }
  }

  // mirrored div
  var div = document.createElement('div');
  div.id = 'input-textarea-caret-position-mirror-div';
  document.body.appendChild(div);

  var style = div.style;
  var computed = window.getComputedStyle? getComputedStyle(element) : element.currentStyle;  // currentStyle for IE < 9

  // default textarea styles
  style.whiteSpace = 'pre-wrap';
  if (element.nodeName !== 'INPUT')
    style.wordWrap = 'break-word';  // only for textarea-s

  // position off-screen
  style.position = 'absolute';  // required to return coordinates properly
  if (!debug)
    style.visibility = 'hidden';  // not 'display: none' because we want rendering

  // transfer the element's properties to the div
  properties.forEach(function (prop) {
    style[prop] = computed[prop];
  });

  if (isFirefox) {
    // Firefox lies about the overflow property for textareas: https://bugzilla.mozilla.org/show_bug.cgi?id=984275
    if (element.scrollHeight > parseInt(computed.height))
      style.overflowY = 'scroll';
  } else {
    style.overflow = 'hidden';  // for Chrome to not render a scrollbar; IE keeps overflowY = 'scroll'
  }

  div.textContent = element.value.substring(0, position);
  // the second special handling for input type="text" vs textarea: spaces need to be replaced with non-breaking spaces - http://stackoverflow.com/a/13402035/1269037
  if (element.nodeName === 'INPUT')
    div.textContent = div.textContent.replace(/\s/g, '\u00a0');

  var span = document.createElement('span');
  // Wrapping must be replicated *exactly*, including when a long word gets
  // onto the next line, with whitespace at the end of the line before (#7).
  // The  *only* reliable way to do that is to copy the *entire* rest of the
  // textarea's content into the <span> created at the caret position.
  // for inputs, just '.' would be enough, but why bother?
  span.textContent = element.value.substring(position) || '.';  // || because a completely empty faux span doesn't render at all
  div.appendChild(span);

  var coordinates = {
    top: span.offsetTop + parseInt(computed['borderTopWidth']),
    left: span.offsetLeft + parseInt(computed['borderLeftWidth'])
  };

  if (debug) {
    span.style.backgroundColor = '#aaa';
  } else {
    document.body.removeChild(div);
  }

  return coordinates;
}

if (typeof module != 'undefined' && typeof module.exports != 'undefined') {
  module.exports = getCaretCoordinates;
} else if(isBrowser){
  window.getCaretCoordinates = getCaretCoordinates;
}

}());
</script>

And this code of id by https://github.com/component/textarea-caret-position. Thanks for him...

LIMITATION:

Its only giving coordinate with respect to element but I want to get it with respect to whole document...

To fix this limitation, I added another function that will find out element coordinate with respect to whole document so just add the below function also...

<script type="text/javascript">
/* Get Element XY Coordinate
----------------------------------------------- */
function getElementCoords(elem) { // crossbrowser version
    var box = elem.getBoundingClientRect();

    var body = document.body;
    var docEl = document.documentElement;

    var scrollTop = window.pageYOffset || docEl.scrollTop || body.scrollTop;
    var scrollLeft = window.pageXOffset || docEl.scrollLeft || body.scrollLeft;

    var clientTop = docEl.clientTop || body.clientTop || 0;
    var clientLeft = docEl.clientLeft || body.clientLeft || 0;

    var top  = box.top +  scrollTop - clientTop;
    var left = box.left + scrollLeft - clientLeft;

    return { top: Math.round(top), left: Math.round(left) };
}
</script>

So finally our Main Function will be now as...

<script type="text/javascript">
/* Main Function
----------------------------------------------- */
function myFunction(Desired_ID){
    // Extra Codes Here ETC...
    document.getElementById(Desired_ID.id).style.backgroundColor = "red";
    // Extra Codes Here ETC...
    var coordinates = getCaretCoordinates(Desired_ID, Desired_ID.selectionStart);
    var elementCoordinates = getElementCoords(Desired_ID);
    var topPosition = coordinates.top + elementCoordinates.top;
    var leftPosition = coordinates.left + elementCoordinates.left;
    alert(leftPosition + ", " + topPosition);
    // Extra Codes Here ETC...
}
</script>

SO finally our last DEMO is at https://jsfiddle.net/qjkkqdg2/2/