Live Пример:
JS
$('#addContent').append('<input type="text" value="Default Value" id="newContent" />');
alert('Adding Dynamic content/element');
$('#newContent').val('Hello new Value 123');
alert('Changing the value');
$('#home').trigger('create');
alert('Refreshing JQM controls and look');
HTML
<div data-role="page" id="home">
<div data-role="content">
<div id="addContent">
<!-- Add Dynamic content here -->
</div>
</div>
</div>
ОБНОВЛЕНИЕ Из вашего комментария
JS
$("#btn1").click(function() {
$('#txtContent').attr('data-theme','e').removeClass('ui-body-d').addClass('ui-body-e').trigger('create');
});
$("#btn2").click(function() {
alert("Theme = " + $('#txtContent').attr('data-theme'));
});
HTML
<div data-role="page" id="home">
<div data-role="content">
<div id="addContent">
<p><input type="text" value="I want to copy you" data-theme="d" id="txtContent" /></p>
<p><input type="text" value="Try to look like me" data-theme="e" id="txtContent2" /></p>
<p><button id="btn1">Change theme</button></p>
<p><button id="btn2">View theme</button></p>
<!-- Add Dynamic content here -->
</div>
</div>
</div>