动态插入script标签并监听加载

function callback() {
}

    // 插入script标签并监听加载
    var head = document.getElementsByTagName('head')[0];
    var script = document.createElement('script');
    script.type= 'text/javascript';
    script.onload = script.onreadystatechange = () => {
      if (!this.readyState || this.readyState === "loaded" 
                                    || this.readyState === "complete" ) {
        callback();
        // Handle memory leak in IE
        script.onload = script.onreadystatechange = null;
      }
    };
    script.src= scriptSrc;
    head.appendChild(script);

作者：anefish
链接：https://www.jianshu.com/p/232ba8260298