Use markdown converter to convert markdown text to html data. Below is the code
// create a pagedown converter - regular and sanitized versions are both supported
var converter = new Markdown.Converter();
// tell the converter to use Markdown Extra
Markdown.Extra.init(converter);
var $txtLabel = $('.cposttext');
$.each($txtLabel, function (index, item) {
$(this).html(converter.makeHtml($(this).html()));
});
<script src="../Scripts/pagedown/Markdown.Extra.js" type="text/javascript"></script>