<script type="text/javascript">
    mui.init();
    mui.plusReady(function() {
        document.getElementById("btn").addEventListener("click", function() {
            document.querySelector(".mui-modal").classList.add("mui-active");
        });
        document.getElementById("modal_close").addEventListener("click", function() {
            document.querySelector(".mui-modal").classList.remove("mui-active");
        });
    });
</script>

相关资料

mui的modal能不能通过脚本控制

github-examples-modals.html