BackgroundFetchRegistration.onprogress

The onprogress EventHandler of the BackgroundFetchRegistration interface is an event handler that processes background fetch events.

The event fires when any of the following properties change:

• uploaded
• downloaded
• result
• failureReason

Syntax

BackgroundFetchRegistration.onprogress = function;
BackgroundRegistration.addEventListener('progress', function);

Where function is the JavaScript function to execute.

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