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The onChanged() event of the downloads API is fired when any of a downloads.DownloadItem's properties changes (except for bytesReceived).

The listener is passed a downloadDelta as a parameter — an object containing the downloadId of the downloads.DownloadItem object in question, plus the status of all the properties that changed.

Syntax

browser.downloads.onChanged.addListener(listener)
browser.downloads.onChanged.removeListener(listener)
browser.downloads.onChanged.hasListener(listener)

Events have three functions:

addListener(callback)
Adds a listener to this event.
removeListener(listener)
Stop listening to this event. The listener argument is the listener to remove.
hasListener(listener)
Check whether a given listener is registered for this event. Returns true if it is listening, false otherwise.

addListener syntax

Parameters

callback

A callback function that will be called when this event occurs. This function will be passed the following arguments:

downloadDelta
An object representing the downloads.DownloadItem object that changed, and the status of all the properties that changed in it.

Additional objects

downloadDelta

The downloadDelta object has the following properties available:

id
An integer representing the id of the downloads.DownloadItem that changed.
urlOptional
A downloads.StringDelta object describing a change in a downloads.DownloadItem's url.
filenameOptional
A downloads.StringDelta object describing a change in a downloads.DownloadItem's filename.
dangerOptional
A downloads.StringDelta object describing a change in a downloads.DownloadItem's danger.
mimeOptional
A downloads.StringDelta object describing a change in a downloads.DownloadItem's mime.
startTimeOptional
A downloads.StringDelta object describing a change in a downloads.DownloadItem's startTime.
endTimeOptional
A downloads.StringDelta object describing a change in a downloads.DownloadItem's endTime.
stateOptional
A downloads.StringDelta object describing a change in a downloads.DownloadItem's state.
canResumeOptional
A downloads.BooleanDelta object describing a change in a downloads.DownloadItem's canResume status.
pausedOptional
A downloads.BooleanDelta object describing a change in a downloads.DownloadItem's paused status.
errorOptional
A downloads.StringDelta object describing a change in a downloads.DownloadItem's error status.
totalBytesOptional
A downloads.DoubleDelta object describing a change in a downloads.DownloadItem's totalBytes.
fileSizeOptional
A downloads.DoubleDelta object describing a change in a downloads.DownloadItem's fileSize.
existsOptional
A downloads.BooleanDelta object describing a change in a downloads.DownloadItem's exists status.

Browser compatibility

ChromeEdgeFirefoxFirefox for AndroidOpera
Basic supportYesNo4748Yes

Examples

Log a message when downloads complete:

function handleChanged(delta) {
  if (delta.state && delta.state.current === "complete") {
    console.log(`Download ${delta.id} has completed.`);
  }
}

browser.downloads.onChanged.addListener(handleChanged);

Acknowledgements

This API is based on Chromium's chrome.downloads API.

Microsoft Edge compatibility data is supplied by Microsoft Corporation and is included here under the Creative Commons Attribution 3.0 United States License.

Document Tags and Contributors

 Contributors to this page: wbamberg, Makyen, chrisdavidmills
 Last updated by: wbamberg,