JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://code.jquery.com/mobile/1.0b1/jquery.mobile-1.0b1.min.css">
<script src="http://code.jquery.com/mobile/1.0b1/jquery.mobile-1.0b1.min.js"></script>
<div data-role="page">
     <div data-role="content">
          <div data-role="fieldcontain">
                <input type="search" name="postcode" id="postcode" value="" data-inline="true" /><input id="btnUpdatePostcode" type="button" value="Update" data-inline="true">
            </div>
    </div>
</div>

CSS

.ui-input-search {
    width: 50px;
    display: inline-block;
}

.ui-field-contain {
    border-bottom-width: 0;
}