sHTML += '<div id="myModal" class="modal">';
sHTML += '<div class="modal-content"><p>some text in modal</p></div>';
sHTML += '</div>';
$("Body").append( sHTML );

$(".modal").css({"display":"none","position":"fixed","z-index":"1","padding-top":"100px","left":"0","top":"0","width":"100%","height":"100%","overflow":"auto","background-color":"rgb(0,0,0)","background-color":"rgba(0,0,0,0.4)"});

$("#documentLink").on('click', function() {
    var modal = document.getElementById('myModal');
    modal.style.display = "block";

    //processing logic...

    //processing finished.

    modal.style.display = "none";
});