javascript jquery deferred 无法与worker一起使用？

Question

我有以下 JavaScript 代码:

var promises = [];

    // Entries contains an unknown amount of items. For the sake of this
    // sample, it has five.
$.each(entries, function() {
    promises.push(doProcessing());
});

return $.when.apply($, promises).done(function() {
    alert('success');
}).fail(function() {
    alert('failed');
});

如果我的 doProcessing 函数是:

function doProcessing() {
    var def = $.Deferred();

    setTimeout(function () {
        console.log('Request completed');
        def.resolve();
    },2000);

    return def.promise();
} // End of doProcessing

我收到五次请求已完成日志，然后是“成功”警报。如果我将 doProcessing 方法更改为:

function doProcessing() {
    var def = $.Deferred();

    // Worker has a message
    myWorker.onmessage = function(event) {
      console.log('Worker finished');
      def.resolve();
      console.log(def);
    };

    myWorker.postMessage({action:'doSomething'});

    return def.promise();
} // End of doProcessing

如果我的工作人员现在正在进行一些处理并解决延迟问题，那么我将不再收到成功警报。我确实收到了五条 Worker finish 消息，并且我的 def 对象也已注销。

我不确定我在这里做错了什么。有人能指出我正确的方向吗？

Answer 1

I DO get five Worker finished messages, and my def object is also logged out.

但它是同一个 def 对象。通过

 myWorker.onmessage = function(event) {
     …
 }

您正在覆盖 .onmessage 属性，并且只有最后一个监听器将被所有 5 个事件调用。相反，做类似的事情

worker.messages = 0;
function doProcessing() {
    var def = $.Deferred(),
        id = worker.messages++;

    // Worker has a message
    myWorker.addEventListener("message", function l(event) {
        if (event.data.id != id) return; // It's not for us!
        console.log('Worker '+id+' finished');
        def.resolve(event.data);
        worker.removeEventListener(l);
    });

    myWorker.postMessage({action:'doSomething', id:id});

    return def.promise();
}

并调整工作代码，以便将 id 传回。