Imprima uma div específica em JavaScript

function PrintElem(elem) {
    const mywindow = window.open('', 'PRINT', 'height=400,width=600');

    mywindow.document.write('<html><head><title>' + document.title  + '</title>');
    mywindow.document.write('</head><body >');
    mywindow.document.write('<h1>' + document.title  + '</h1>');
    mywindow.document.write(document.getElementById(elem).innerHTML);
    mywindow.document.write('</body></html>');
    mywindow.document.close(); // necessary for IE >= 10
    mywindow.focus(); // necessary for IE >= 10*/
    mywindow.print();
    mywindow.close();
    return true;
}
Wissam