files/en-us/mozilla/add-ons/webextensions/api/downloads/onchanged/index.md
The onChanged() event of the {{WebExtAPIRef("downloads")}} API is fired when any of a {{WebExtAPIRef('downloads.DownloadItem')}}'s properties changes (except for bytesReceived).
The listener is passed a downloadDelta as a parameter — an object containing the downloadId of the {{WebExtAPIRef('downloads.DownloadItem')}} object in question, plus the status of all the properties that changed.
browser.downloads.onChanged.addListener(listener)
browser.downloads.onChanged.removeListener(listener)
browser.downloads.onChanged.hasListener(listener)
Events have three functions:
addListener(listener)
removeListener(listener)
listener argument is the listener to remove.hasListener(listener)
listener is registered for this event. Returns true if it is listening, false otherwise.listener
downloadDelta
object representing the {{WebExtAPIRef('downloads.DownloadItem')}} object that changed, and the status of all the properties that changed in it. See the downloadDelta section for more details.The downloadDelta object has the following properties available:
id
integer representing the id of the {{WebExtAPIRef('downloads.DownloadItem')}} that changed.url {{optional_inline}}
url.filename {{optional_inline}}
filename.danger {{optional_inline}}
danger.mime {{optional_inline}}
mime.startTime {{optional_inline}}
startTime.endTime {{optional_inline}}
endTime.state {{optional_inline}}
state.canResume {{optional_inline}}
canResume status.paused {{optional_inline}}
paused status.error {{optional_inline}}
error status.totalBytes {{optional_inline}}
totalBytes.fileSize {{optional_inline}}
fileSize.exists {{optional_inline}}
exists status.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);
{{WebExtExamples}}
{{Compat}}
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chrome.downloadsAPI.