两种方法动态加载外部原生JS文件

//方法1----------------------------------------
    document.write("<script src='js/external.js'><\/script>");
    
    //方法2----------------------------------------
    /** 
    动态加载JS 
    @param {string} url 脚本地址
    @param {function} callback  回调函数 
    */
    function loadJS(url, callback) {
        let script = document.createElement("script");
        script.type = "text/javascript";
        script.src = url;
        if (typeof (callback) === "function") {
            script.onload =
                script.onreadystatechange = function () {
                    if (!this.readyState || this.readyState === "loaded" || this.readyState === "complete") {
                        callback();
                        script.onload = script.onreadystatechange = null;
                    }
                };
        }
        document.querySelector("html").appendChild(script);
    }