XMLHttpRequest级别2-确定上传是否完成

Question

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）-对于较大的文件，这需要花费几秒钟的时间。当文件上传时，<progress>正在填充HTML5
，当文件准备好并且PHP开始检查时，进度应该切换为不确定。我认为对的方式来做到这一点（这两者做 不 工作）：

检查upload.onload事件

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

这行不通，因为onload-event在请求准备就绪时触发，而不是在上传准备就绪时触发。

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 + "%");
        }
   }
}
});

这是行不通的，因为上载百分比有时会停在大约 97％，尽管上传完成并且PHP开始处理文件

还有另一种可能性检查吗？

Answer 1

您要监听的事件readystatechange在XHR对象上（不在XHR.upload上）。readyState是4当上载完成发送 ，并
在服务器关闭连接 。loadend/ load在上载完成时触发，无论服务器是否关闭连接。仅供参考，以下是您可以收听以及触发的事件：

    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.
      }
    });