javascript - XmlHttpRequest onprogress 间隔

Question

我正在使用 XmlHttpRequests 将图像上传到服务器，我想向用户显示这些上传的进度。

不幸的是，对我的 onprogress-event 处理程序的调用之间的间隔太大。对于 500k 的图像，onprogress 通常只调用一次或两次。

这是我的代码:

/* This function is not called often enough */
function progress(e){
    console.log('Uploading: ' + Math.round((e.loaded / e.total) * 100) + ' %');
}

var xhr = new XMLHttpRequest();
xhr.upload.addEventListener('progress', progress, false);
xhr.send(data);

是否可以更改此行为或者是否在浏览器实现中的某处进行了硬编码？

Answer 1

W3 在其 XMLHttpRequest Level 2 中提出了以下准则文档。显然，不同浏览器的一致性水平是可以预料的。

上传:

While the request entity body is being uploaded and the upload complete flag is false, queue a task to fire a progress event named progress at the XMLHttpRequestUpload object about every 50ms or for every byte transmitted, whichever is least frequent. - W3 XMLHttpRequest Level 2 (Bolded for emphasis)

下载:

When it is said to make progress notifications, while the download is progressing, queue a task to fire a progress event named progress about every 50ms or for every byte received, whichever is least frequent. - W3 XMLHttpRequest Level 2 (Bolded for emphasis)

我不知道可以自定义此功能的 API。