Edit in JSFiddle

 clearCache = function(){
    l=function(){
        setTimeout(function(){
            var a=window.frames['fcc'].location.pathname.split('/');
            if(a[a.length-2]=='newhtml.html'){
                f.style.display='none';
                m.setAttribute('style',lol+'background:#093;border:1px solid #093;color:#FFF');
                d.innerHTML='Success!';
                window.location.reload();
    
                console.log('Success!');
            }else{
                f.style.display='block';
                m.setAttribute('style',lol+'background:#C00;border:1px solid #C00;color:#FFF');
                d.innerHTML='Authorization...';
    
                console.log('Authorization...');
            }
        },100);
    };
    var lol='position:fixed;z-index:9999;top:9px;left:50%;margin-left:-128px;width:256px;box-shadow:0 2px 4px rgba(0,0,0,0.2);border-radius:2px;text-align:center;font:14px/25px sans-serif;overflow:hidden;';
    if(!document.getElementById('mcc')){
        var m=document.createElement('div');
        var f=document.createElement('iframe');
        var d=document.createElement('div');
    
        m.setAttribute('style',lol+'background:#F9EDBE;border:1px solid #F0C36D;color:#000');
        m.setAttribute('id','mcc');
    
        f.setAttribute('name','fcc');
        f.setAttribute('id','fcc');
        f.setAttribute('onLoad','l();');
        f.setAttribute('src','newhtml1.html/');
        f.setAttribute('style','display:none;border:none;height:290px;width:100%');
    
        d.setAttribute('style','cursor:pointer');
        d.setAttribute('onclick','document.getElementById(\'mcc\').style.display=\'none\';return false');
    
        d.innerHTML='Clearing Cache...';
        m.appendChild(d);
        m.appendChild(f);
        document.body.appendChild(m);
    
        console.log('Create block');
    }else{
        var m=document.getElementById('mcc');
        var d=m.getElementsByTagName('div')[0];
        var f=document.getElementById('fcc');
        m.style.display='block';
    
        console.log('Init block');
    }
} 
 <button type="button" onclick="clearCache();">clear cache</button>