javascript 动态加载javascript文件

    /*
        loadFile(data, callback): 动态加载js文件
        data: 存放需要加载的js文件的url("url" || ["url", "url"])
        callback: 加载完成回调函数
    */
    function loadFile(data, callback){
        if(!data){return;}
        let k, arr = [], el = document.body;
        if(typeof(data) === 'string'){arr.push(data);}
        else if(Array.isArray(data) === true){for(k in data){arr.push(data[k]);}}
        else{return;}
        
        let load = (url, suc, err)=>{
            let script = document.createElement('script');
            script.type = "text/javascript";//type = 'module';
            script.src = url;
            el.appendChild(script);
            script.onload = function (e){if(typeof(suc) === "function"){suc(e);}}
            script.onerror = function (e){if(typeof(err) === "function"){err(e);}}
        }
        
        let timeout = ()=>{
            if(t === len){if(typeof(callback) === "function"){callback(t, len, arr);} return;}
            setTimeout(timeout, 1000);
        }
        
        let len = arr.length, t = 0;
        for(k in arr){load(arr[k], (e)=>{t++;});}
        timeout();
    }
    //调用
    loadFile("./main.js", (t, len, arr)=>{document.write(t+" "+len+" "+arr)});
    loadFile(["./main.js", "./init.js"], (t, len, arr)=>{document.write(t+" "+len+" "+arr)});