JavaScript 中如何加载远程脚本

var head = document.getElementsByTagName('head')[0];
    var script = document.createElement('script');
    script.setAttribute('type', 'text/javascript');
    script.setAttribute('src', url);
    head.appendChild(script);
    //加载成功
    var onLoadSuccess = () => {
      
    }
    if (document.all) { //IE
        script.onreadystatechange = function () {
            if (script.readyState == 'loaded' || script.readyState == 'complete') {
                onLoadSuccess();
            }
        }
    } else {
        script.onload = function () {
            onLoadSuccess();
      }
    }