JSFiddle - React, Tailwind, and code Playground

HTML

<div id="text" contentEditable="true" >hello world</div>

<button onclick="myFunction()"  >Emoji </button>

CSS

#text {  body {
      font-family: Helvetica, sans-serif;
      color: #333;
    }
    #text_wrapper {
      margin: 40px;

    }
      outline: none;
      margin: 10px;
      min-height:200px;
    }

JavaScript

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 myFunction() {
				var c=document.getElementById("text"); 
				var position = getCaretCharacterOffsetWithin(c);
        var text = c.innerHTML;
        var imgStr = '<img src="1f602.png" width="20" />'
        c.innerHTML = text.slice(0,position) + imgStr + 		text.slice(position,text.length);
    }