ProgressEvent: ProgressEvent() constructor

type

A string with the name of the event. It is case-sensitive and browsers set it to loadstart, progress, abort, error, load, timeout, or loadend.

options Optional

An object that, in addition of the properties defined in Event(), can have the following properties:

lengthComputable Optional

A boolean value indicating if the total work to be done, and the amount of work already done, by the underlying process is calculable. In other words, it tells if the progress is measurable or not. It defaults to false.

loaded Optional

A number representing the amount of work already performed by the underlying process. The ratio of work done can be calculated with the property and ProgressEvent.total. When downloading a resource using HTTP, this only represent the part of the content itself, not headers and other overhead. It defaults to 0.

total Optional

A number representing the total amount of work that the underlying process is in the progress of performing. When downloading a resource using HTTP, this only represent the content itself, not headers and other overhead. It defaults to 0.

A new ProgressEvent object.

The example demonstrates how a ProgressEvent is built using a constructor. This is particularly useful for tracking the progress of processes like file uploads, downloads, or any long-running tasks.

function updateProgress(loaded, total) {
  const progressEvent = new ProgressEvent("progress", {
    lengthComputable: true,
    loaded: loaded,
    total: total,
  });

  document.dispatchEvent(progressEvent);
}

document.addEventListener("progress", (event) => {
  console.log(`Progress: ${event.loaded}/${event.total}`);
});

updateProgress(50, 100);

• The ProgressEvent interface it belongs to.