javascript - XMLHttpRequest Level 2 - 确定上传是否完成

Question

我使用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，这需要几秒钟的时间。上传文件时，会出现 HTML5 <progress>正在填充，当文件准备好并且 PHP 开始检查时，进度应切换为不确定。我想到了一些方法来做到这一点(这两种方法都不起作用):

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。

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%，尽管上传已完成且 PHP 开始处理文件

还有其他可能性检查这个吗？

Answer 1

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

    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.
      }
    });