HTML 5: Spellcheck Attribute

HTML

<!DOCTYPE html>
<html>
<head></head>
<body>
    <header>
        <h1>
            HTML 5: Spellcheck
            (<span id="support">Your browser does not support spellcheck attribute</span>)
        </h1>
    </header>
    <article>
        <div>
                  
        </div>
        <textarea lang="da" spellcheck="true" placeholder="spellcheck='true'"></textarea>
        <textarea spellcheck="false" placeholder="spellcheck='false'"></textarea>
    </article>    
</body>
</html>

CSS

body{
    font-family: "Verdana";
    font-size: 9pt;
}

header{
    padding: 15px;
    background-color: rgb(27, 161, 226);
    box-shadow: 0px 1px 2px rgba(0,0,0,0.4);
    color: #fff;
}

header h1{
    font-size: 12pt;
}

article{
    width: 80%;
    margin: auto;
    margin-top: 20px;
}

article textarea{
    width: 400px;
    height: 200px;
}

#support{
   padding: 5px;
   color: red;
}

#spellLabel{
    color: green;
}

JavaScript

window.onload = function(){
    
    var support = document.getElementById("support");
    
    if('spellcheck' in document.createElement('textarea'))
    {
        support.textContent = "Your browser supports spellcheck";
        support.style.color = "green";
    }
}