Question

我有10个js文件。我在加载java类之前加载所有文件。但我需要检查所有文件是否正确加载然后我调用我的java类。

首先我调用一个js文件加载我所有必需的js文件，这里我需要检查我所有正确加载的10个js文件然后我需要调用一个函数。

这是我的代码

loadpackage("0.js",callback);
loadpackage("1.js",callback);
loadpackage("2.js",callback);
loadpackage("3.js",callback);
loadpackage("4.js",callback);
loadpackage("5.js",callback);
loadpackage("6.js",callback);
loadpackage("7.js",callback);
loadpackage("8.js",callback);
loadpackage("9.js",callback);
loadpackage("10.js",callback);


function loadpackage(path, callback) {

    var done = false;
    var scr = document.createElement('script');

    scr.onload = handleLoad;
    scr.onreadystatechange = handleReadyStateChange;
    scr.onerror = handleError;
    scr.src = path;
    document.body.appendChild(scr);

    function handleLoad() {
        if (!done) {
            done = true;
            callback(path, "ok");
        }
    }

    function handleReadyStateChange() {
        console.log("readystate1");
        var state;

        if (!done) {
            console.log("readystate2");
            state = scr.readyState;
            console.log("readystate3");
            if (state === "complete") {
                console.log("readystate4");
                handleLoad();
            }
        }
    }
    function handleError() {
        if (!done) {
            done = true;
            callback(path, "error");
        }
    }
}

function callback(path, message) {
    console.log(path+" :: "+message);
}

我在某些地方读到onreadystatechange事件表示文件已成功加载但未调用onreadystatefunction。

所以请帮我解决这个问题，如何检查我的所有10个js文件是否正确加载。

有些问题使用jQuery回答了这个问题，但我不能使用jQuery，我需要JavaScript或GWT中的答案

框架：GWT 2.6.0
我正在研究使用Java Class的GWT＆amp;执行一些操作我需要加载js文件

Answer 1

创建一些计数器，然后每次onload回调激活时减少它。当它达到0时，做你需要的。

var scripts = ['1.js', '2.js', ...]
var scriptsToLoad = scripts.length

scripts.forEach(loadScript)

function loadScript (path) {
  var scr = document.createElement('script')

  scr.onload = function () {
    scriptsToLoad -= 1

    if (scriptsToLoad === 0) doYourJavaThing()
  }

  scr.src = path
  document.body.appendChild(scr)
}

function doYourJavaThing () {
  // la la la
}

Answer 2

正如我所看到的，在这种情况下你将不得不使用Promise，这意味着你的函数加载脚本会非常方便地返回这样的承诺：

//Change your function to this:
function loadpackage( path, resolve, reject ) {

    var done = false;
    var scr = document.createElement('script');

    scr.onload = handleLoad;
    scr.onreadystatechange = handleReadyStateChange;
    scr.onerror = handleError;
    scr.src = path;
    document.body.appendChild(scr);

    function handleLoad() {
        if (!done) {
            done = true;
            resolve( { path:path,status:'ok' } );
        }
    }

    function handleReadyStateChange() {
        console.log("readystate1");
        var state;

        if (!done) {
            console.log("readystate2");
            state = scr.readyState;
            console.log("readystate3");
            if (state === "complete") {
                console.log("readystate4");
                handleLoad();
            }
        }
    }
    function handleError() {
        if (!done) {
            done = true;
            reject( { path:path,status:'error' } );
        }
    }
}

//Use promises


var promises = [];

promises.push( new Promise( function( resolve,reject ){

    loadpackage( "0.js", resolve, reject )

}) );
promises.push( new Promise( function( resolve,reject ){

    loadpackage( 'path', resolve, reject )

}) );
promises.push( new Promise( function( resolve,reject ){

    loadpackage( "1.js", resolve, reject )

}) );

//...etc

//And finally wait untill all of them are resolved

Promise.all( promises ).then( function( value ){

    //Here you absolutely know that all files have loaded, 
    //and you can fire callback here for each of them like

    callbak( value.path, value.status );

});

检查Javascript正确加载

2 个答案: