JSFiddle - React, Tailwind, and code Playground

HTML

<div id="editor" contenteditable="true">
I am some text.
</div>

CSS

body {
    background: #EEE;
}

#editor {
    background: #FFF;
    width: 200px;
    height: 90px;
    overflow: auto;
}

JavaScript

function insertNodeBeforeCaret(node) {
    if (typeof window.getSelection != "undefined") {
        var sel = window.getSelection();
        if (sel.rangeCount) {
            var range = sel.getRangeAt(0);
            range.collapse(false);
            range.insertNode(node);
            range = range.cloneRange();
            range.selectNodeContents(node);
            range.collapse(false);
            sel.removeAllRanges();
            sel.addRange(range);
        }
    } else if (typeof document.selection != "undefined" && document.selection.type != "Control") {
        var html = (node.nodeType == 1) ? node.outerHTML : node.data;
        var id = "marker_" + ("" + Math.random()).slice(2);
        html += '<span id="' + id + '"></span>';
        var textRange = document.selection.createRange();
        textRange.collapse(false);
        textRange.pasteHTML(html);
        var markerSpan = document.getElementById(id);
        textRange.moveToElementText(markerSpan);
        textRange.select();
        markerSpan.parentNode.removeChild(markerSpan);
    }
}

$("#editor").keydown(function(event){
    if(event.which == 50 && event.shiftKey){ // 50 => '2' and shift+'2' => @
        event.preventDefault(); // abort inserting the '@'
        var html = $('<span>hi</span>'); // create html node
        insertNodeBeforeCaret(html[0]); // insert node before caret
    }
});