Edit in JSFiddle

$(document).ready(function () {
    $(document).on('click', '#setHtml', function (event) {
        var content = $(".test").html(function(){
      return "New Content"; 
    });
});
});

<h1>function with jquery html()</h1>

<div class="test">This is test class</div>

<input type="submit" value="set Html" id="setHtml" />