Edit in JSFiddle

$(document).ready(function () {
    $(document).on('click', '#setHtml', function (event) {
        var content = $(".test").html("<b>Replaced content</b>");
    });
});

<h1>Jquery html() to set all the selector</h1>

<div class="test">This is test class of first div</div>
<div class="test">This is test class of second div</div>
<div class="test">This is test class of third div</div>
<input type="submit" value="set Html" id="setHtml" />