在 Javascript 中使用 Fetch API 上传文件并显示进度

问题描述

我在 Javascript 中使用 Fetch API将大文件上传到服务器.Fetch API 中是否有任何事件可用于跟踪上传进度?

I'm using Fetch API in Javascript to upload big file to server. Is there any event in Fetch API that I could use to track progress of upload?

推荐答案

这不可能.原因在于 Fetch API 的工作方式.

This is NOT possible. The reason is the way the Fetch API works.

fetch 方法返回一个 Promise；Promise API 使用 then 方法，您可以将成功"和失败"回调附加到该方法.因此，您可以获得进度.

The fetch method returns a Promise; the Promise API uses a then method to which you can attach "success" and "failure" callbacks. Therefore, you can gain access to progress.

不过，不要失去希望！有一种解决方法可以解决问题(我在 Fetch 的 github 存储库中找到了它API):

Still, don't lose hope! There is a workaround that can do the trick (I found it on github repository of the Fetch API):

您可以将请求转换为流请求，然后在响应返回时只是文件内容的位数组.那么您需要收集所有数据，并在其结束时将其解码为您想要的文件

you can convert the request to a stream request and then when a response return is just a bitarray of the file content. then you need to collect all of the data and when its end decode it to the file you want

function consume(stream, total = 0) {
  while (stream.state === "readable") {
    var data = stream.read()
    total += data.byteLength;
    console.log("received " + data.byteLength + " bytes (" + total + " bytes in total).")
  }
  if (stream.state === "waiting") {
    stream.ready.then(() => consume(stream, total))
  }
  return stream.closed
}
fetch("/music/pk/altes-kamuffel.flac")
  .then(res => consume(res.body))
  .then(() => console.log("consumed the entire body without keeping the whole thing in memory!"))
  .catch((e) => console.error("something went wrong", e))

这篇关于在 Javascript 中使用 Fetch API 上传文件并显示进度的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持编程学习网！