BackgroundFetchRegistration: progress event

Limited availabilityAvailable in workers

The progress event of the BackgroundFetchRegistration interface thrown when the associated background fetch progresses.

Practically, this event is fired when any of the following properties will return a new value:

• uploaded,
• downloaded,
• result, or
• failureReason.

Syntax

Use the event name in methods like addEventListener(), or set an event handler property.

addEventListener("progress", (event) => { })

onprogress = (event) => { }

Event type

A generic Event with no added properties.

Example

The following example demonstrates how to log the progress of a download. The code first checks that a downloadTotal was provided when the background fetch was registered. This is then used to calculate the percentage, based on the downloaded property.

bgFetch.addEventListener("progress", () => {
  if (!bgFetch.downloadTotal) return;
  const percent = Math.round(
    (bgFetch.downloaded / bgFetch.downloadTotal) * 100,
  );
  console.log(`Download progress: ${percent}%`);
});

Specifications

Browser compatibility