my-index.ejs

<!DOCTYPE html>
<html class="cbioportal-frontend">
<head>
    <meta http-equiv="Content-type" content="text/html; charset=utf-8"/>
    <link rel="icon" href="/images/cbioportal_icon.png"/>
    <title>cBioPortal for Cancer Genomics</title>
    <script>

        window.devContext = true;
        window.frontendConfig = {
        }

        localStorage.frontendConfig = JSON.stringify(
            {
                serverConfig:{

                       custom_tabs:[
 {
            title: 'Sync Tab',
            id: 'customTab1',
            location: 'PATIENT_PAGE',
            mountCallback: `(div)=>{
                    $(div).html("tab for patient " + window.location.search.split("=").slice(-1))
                }`,
        },
        {
            title: 'Async Tab',
            id: 'customTab2',
            location: 'PATIENT_PAGE',
            hideAsync: `()=>{
                           return new Promise((resolve)=>{
                                setTimeout(()=>{
                                    resolve(true);
                                }, 2000);
                           });
                    }`,
        },
                                           ]

                }

           }
        );

    function renderCustomTab1(div, tab){
        $(div).append(`<div>this is the content for <strong>${tab.title}</strong></div>`);
    }


    </script>
    <script src="/reactapp/common.bundle.js"></script>

    <link href="/reactapp/prefixed-bootstrap.min.css" rel="stylesheet"></link>
    <link href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.css" rel="stylesheet" />
</head>
<body>

<div id="reactRoot"></div>

</body>
</html>