Add jQuery to a third party web site

code.js

function l(u, i) {
    var d = document;
    if (!d.getElementById(i)) {
        var s = d.createElement('script');
        s.src = u;
        s.id = i;
        d.body.appendChild(s);
    }
}
l('//code.jquery.com/jquery-3.2.1.min.js', 'jquery')