XMLHttpRequest Level 2 - 确定上传是否完成

问题描述

我正在使用 ajax 进行文件上传.文件上传后，php 应该检查它(mime、大小、病毒(clamscan)等等)——对于较大的文件，这需要几秒钟.当文件上传时，一个 HTML5 <progress> 正在填充，当文件准备好并且 PHP 开始检查时，进度应该切换到不确定.我想到了这样做的方法(两者都不工作):

I am using ajax for file uploads. After the file is uploaded, php should check it (mime, size, virus (clamscan) and more) - this takes some seconds for larger files. While the file is uploading, a HTML5 <progress> is filling, when the file is ready and PHP starts checking, the progress should switch to indeterminate. I thought of to ways to do this (which both do not work):

检查 upload.onload 事件

xhr.upload.addEventListener("load", function (e) {
    $("#uploadprogress").attr("value", false);
    $("#uploadprogress").attr("max", false);
    $("#progress").text("Checking file...");
});

这不起作用，因为 onload-事件在请求准备好时触发，而不是在上传准备好时触发.

This doesn't work, because the onload-event firest when the request is ready, not when upload is ready.

检查上传进度百分比是否 = 100%

xhr.upload.addEventListener("progress", function (e) {
    if (e.lengthComputable && e) {
        p = (e.loaded / e.total);
        if (p==1) {
            $("#uploadprogress").attr("value", false);
            $("#uploadprogress").attr("max", false);
            $("#progress").text("Checking file...");
        } else {
            var percent = Math.ceil(p * 1000) / 10;
            $("#uploadprogress").val(e.loaded);
            $("#uploadprogress").attr("max", e.total);
            $("#progress").text("Uploading... " + percent + "%");
        }
   }
}
});

这不起作用，因为上传百分比有时会停止在大约.97%，尽管上传完成并且 PHP 开始处理文件

This does not work, because the upload percentage sometimes stops at approx. 97%, despite the upload is finished and PHP starts handling the files

还有其他可能检查这个吗?

Is there another possibility checking this?

推荐答案

您要监听的事件是 XHR 对象上的 readystatechange(不是 XHR.upload 上的).readyState 是 4 当上传完成发送并且 服务器关闭连接.loadend/load 在上传完成时触发，无论服务器是否关闭连接.仅供参考，以下是您可以收听的事件以及它们何时触发:

The event you want to listen to is readystatechange on the XHR object (not on XHR.upload). readyState is 4 when the upload has finished sending and the server closes the connection. loadend/load fire when the upload has finished regardless of whether the server closes the connection. Just for reference, here are the events you can listen to and when they fire:

    var xhr = new XMLHttpRequest();

    // ...
    // do stuff with xhr
    // ...

    xhr.upload.addEventListener('loadstart', function(e) {
      // When the request starts.
    });
    xhr.upload.addEventListener('progress', function(e) {
      // While sending and loading data.
    });
    xhr.upload.addEventListener('load', function(e) {
      // When the request has *successfully* completed.
      // Even if the server hasn't responded that it finished.
    });
    xhr.upload.addEventListener('loadend', function(e) {
      // When the request has completed (either in success or failure).
      // Just like 'load', even if the server hasn't 
      // responded that it finished processing the request.
    });
    xhr.upload.addEventListener('error', function(e) {
      // When the request has failed.
    });
    xhr.upload.addEventListener('abort', function(e) {
      // When the request has been aborted. 
      // For instance, by invoking the abort() method.
    });
    xhr.upload.addEventListener('timeout', function(e) {
      // When the author specified timeout has passed 
      // before the request could complete.
    });

    // notice that the event handler is on xhr and not xhr.upload
    xhr.addEventListener('readystatechange', function(e) {
      if( this.readyState === 4 ) {
        // the transfer has completed and the server closed the connection.
      }
    });

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