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：
url 脚本地址
callback  回调函数 
*/
loadJS(url, callback) {
    let script = document.createElement("script");
    script.type = "text/javascript";
    script.src = url;
    script.onload = script.onreadystatechange = function () {
        if (!this.readyState || this.readyState === "loaded" || this.readyState === "complete") {
            callback && callback();
            script.onload = script.onreadystatechange = null;
        }
    };
    document.querySelector("html").appendChild(script);
},