JSFiddle - React, Tailwind, and code Playground

HTML

<h1> Reading Simulator</h1>
<small></small>
<p>Paste or write any text you like and let the bot go throuhg the text in avarage human speed<p>
    <label for="speed">Reading speed in miliseconds:<br/>
        <input type="text" id="speed" value="50" />
    </label>
<div id="sim">
    Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam, eaque ipsa quae ab illo inventore veritatis et quasi architecto beatae vitae dicta sunt explicabo. Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat voluptatem. Ut enim ad minima veniam, quis nostrum exercitationem ullam corporis suscipit laboriosam, nisi ut aliquid ex ea commodi consequatur? Quis autem vel eum iure reprehenderit qui in ea voluptate velit esse quam nihil molestiae consequatur, vel illum qui dolorem eum fugiat quo voluptas nulla pariatur?
</div>
 <!-- <textarea id="sim" value=""></textarea> -->
<br/>
<button id="go" >Go! </button>
<button id="stop">Stop!</button>
<div class="summary" id="summary">
    <p id="wordCountBox"></p>
    <p id="timepassed"></p>
    <p id="textRead"></p>
 </div>

CSS

#sim{
    width:400px;
    height:200px;
    border:solid 1px #2e2e2e;
    color:#2e2e2e;
    padding:5px;
    overflow-y:scroll;
}
button{
    padding:10px 25px;
    color:#fafafa;
    transition:all 0.3s;
    cursor:pointer;
}
#go{
    background-color:#46A111;
    border:solid 1px #46A111;
}
#go:hover{
    background-color:#fafafa;
    color:#46A111;
}
#stop{
    background-color:#A11111;
    border:solid 1px #A11111;
}
#stop:hover{
    background-color:#fafafa;
    color:#A11111;
}
p{
    font-family:Arial;
    font-weight:bold;
    color:#2e2e2e;
    padding:5px 10px;
}
b{
    background-color:yellow;
}
h1, p{
    font-family:"Ubuntu", Arial;
}
p{
    padding:0;
    margin:0;
}
label{
    display:block;
    padding:10px 0;
}
input[type="text"]{
    width:400px;
    height:40px;
    border:solid 1px #2e2e2e;
    padding:0 5px;
}
.summary{
    background-color:rgba(0,0,0,0.1);
    border:solid 1px #2e2e2e;
    padding:10px;
    margin-top:10px;
    display:none;
}

JavaScript

$('#sim').each(function(){
    this.contentEditable = true;
});

var go = $('#go');
var stop = $('#stop');
var wordCount = 0;
var wordCountBox = $('#wordCountBox');
var timepassed = $('#timepassed');
var textRead = $('#textRead');
var small = $('small');


go.on("click", function(e){
    e.preventDefault();
    startSim();
});

function startSim(){
    var speed = $('#speed').val();
    timeStart = $.now();
    var sim = $('#sim').text();
    var wordArray = sim.split(" ");
    var simWrap = $('#sim');
    var loopCount = 0;
    
    var arrCount = wordArray.length;
    var alreadyRead = [];
    loopDat();
    var i = loopCount;    
    function loopDat(){
            var pos = loopCount;
            var realSpeed = wordArray[pos].length;
            realSpeed = (realSpeed * (speed / 5));
            // realSpeed = Math.round((realSpeed * 0.1) * speed);
            console.log('Reading speed of current word: '+realSpeed);
            if(loopCount == pos){
                setTimeout(function() { 
                    if(pos < 0){
                        pos = 0;
                    }
                    alreadyRead.push(wordArray[pos]);
                    wordArray[pos] = '<b>'+wordArray[pos]+'</b>';
                    small.text('Current reading speed: '+realSpeed);
                    var words = wordArray.join(" ");
                    simWrap.html(words);                
                    wordCount++;
                    if(pos == (arrCount - 1)){
                        triggerDone();
                    }
                    loopCount++;
                    if(loopCount < arrCount){
                        loopDat();
                    }
                    $('#sim b:last')[0].scrollIntoView(false);
                }, realSpeed);
            }
    }
    // Function done
    function triggerDone(){
        wordCountBox.text('Words counted: '+wordCount);
        var timeEnd = $.now();
        var timeRes = timeEnd - timeStart;
        timeRes =...