jQuery Deferred notify() Method

What Is notify()?

deferred.notify(args) fires progress callbacks while the Deferred is still pending (since jQuery 1.7). It does not resolve or reject — use it for percent done, step labels, or status text.

dfd.progress(fn)
dfd.notify(25)     // fn(25) — still pending
dfd.notify(50)     // fn(50)
dfd.resolve("ok")  // done handlers; notify stops working

after settle → notify() ignored

How to Use notify()

Attach progress first, call notify during work, then settle.

1. Create a Deferred with $.Deferred().
2. Register .progress(function (value) { ... }) (and usually done / fail).
3. While work runs, call notify(args) one or more times.
4. When finished, resolve or reject — further notify calls are ignored.

Pseudocode

function notify(deferred, args...):
    if deferred is resolved or rejected:
        return deferred          // ignore
    for each progressCallback (in order):
        progressCallback(args...)
    return deferred

Cheat Sheet

Keep these facts handy while wiring progress updates.

Live Preview

Pick a scenario and watch notify() feed progress().

progress: 40%

jQuery Examples

Short, copy-ready snippets. Open DevTools Console, or use Try It Yourself for a live editor.

var dfd = $.Deferred();

dfd.progress(function (pct) {
  console.log("progress: " + pct + "%");
});

dfd.notify(40);
// progress: 40%

progress: 40%

var dfd = $.Deferred();
var lines = [];

dfd.progress(function (pct) {
  lines.push(pct + "%");
});

dfd.notify(25);
dfd.notify(50);
dfd.notify(75);

console.log(lines.join(" → "));
// 25% → 50% → 75%

25% → 50% → 75%

var dfd = $.Deferred();
var lines = [];

dfd
  .progress(function (pct) {
    lines.push("progress: " + pct + "%");
  })
  .done(function (msg) {
    lines.push("done: " + msg);
  });

dfd.notify(50);
dfd.resolve("complete");

console.log(lines.join("\\n"));
// progress: 50%
// done: complete

progress: 50%
done: complete

var dfd = $.Deferred();
var lines = [];

dfd.progress(function (pct) {
  lines.push("progress: " + pct);
});

dfd.resolve("ok");
dfd.notify(99);   // ignored

console.log(lines.length === 0 ? "no progress after resolve" : lines.join("\\n"));
// no progress after resolve

no progress after resolve

Performance Notes

Progress callbacks are cheap, but updating the DOM on every tiny tick can jank. Throttle notifies to meaningful milestones.

Key Takeaways