downloads.DownloadItem

这个类型的值是对象，包含了以下属性：

byExtensionId可选

一个代表了触发此下载的扩展的 ID 的 string （如果是被扩展触发的话）。一旦设置，不会改变。如果下载不是由扩展触发的，则为 undefined。

byExtensionName可选

一个代表了触发此下载的扩展的名字的 string （如果是被扩展触发的话）。如果用户改变了扩展的语言环境，则这个属性的值也可能变化。如果下载不是由扩展触发的，则为 undefined。

bytesReceived

一个代表了在下载过程中从主机接收到的字节数的 number ；不考虑文件压缩。

canResume

一个标识当前中断（例如暂停）的下载是否可以从当前位置恢复的 boolean。

danger

一个标识这个下载是否通过一个不安全的或已知的可疑的站点。可能被设置为 downloads.DangerType 类型。

endTime可选

A string (in ISO 8601 format) representing the number of milliseconds between the UNIX epoch and when this download ended. This is undefined if the download has not yet finished.

error可选

A string indicating why a download was interrupted. Possible values are defined in the downloads.InterruptReason type. This is undefined if an error has not occurred.

estimatedEndTime可选

A string (in ISO 8601 format) representing the estimated number of milliseconds between the UNIX epoch and when this download is estimated to be completed. This is undefined if it is not known (in particular, it is undefined in the DownloadItem that's passed into downloads.onCreated).

exists

A boolean indicating whether a downloaded file still exists (true) or not (false). This information might be out-of-date, as browsers do not automatically watch for file removal — to check whether a file exists, call the downloads.search() method, filtering for the file in question.

filename

A string representing the file's absolute local path.

fileSize

A number indicating the total number of bytes in the whole file, after decompression. A value of -1 here means that the total file size is unknown.

id

An integer representing a unique identifier for the downloaded file that is persistent across browser sessions.

incognito

A boolean that indicates whether the download is recorded in the browser's history (false), or not (true).

mime

A string representing the downloaded file's MIME type.

paused

A boolean indicating whether the download is paused, i.e. if the download has stopped reading data from the host but has kept the connection open. If so, the value is true, false if not.

referrer

A string representing the downloaded file's referrer.

startTime

A string (in ISO 8601 format) representing the number of milliseconds between the UNIX epoch and when this download began.

state

A string Indicating whether the download is progressing, interrupted, or complete. Possible values are defined in the downloads.State type.

totalBytes

A number indicating the total number of bytes in the file being downloaded. This does not take file compression into consideration. A value of -1 here means that the total number of bytes is unknown.

url

A string representing the absolute URL from which the file was downloaded.