jQuery Deferred notify() Method

What You’ll Learn

The notify() method sends progress updates while a jQuery Deferred is still pending. Handlers registered with progress() receive each update — perfect for progress bars, step labels, and status messages before you call resolve() or reject().

Introduction

Not every async task finishes instantly. File uploads, data imports, and multi-step wizards need to tell users something is happening before the final result arrives. jQuery’s notify() method fills that gap — it fires progress() callbacks with status data while the Deferred remains in the pending state.

Think of notify() as a progress ping and resolve() as the finish line. You can ping many times along the way, then resolve when the work truly succeeds (or reject if it fails).

Understanding the notify() Method

notify() is part of jQuery’s Deferred Object API (since jQuery 1.7). Calling deferred.notify(value) invokes every handler attached with progress(), passing along optional arguments — strings, numbers, objects, or multiple values.

Unlike resolve() and reject(), notify() does not settle the Deferred. The state stays pending until you explicitly call resolve() or reject(). After settlement, additional notify() calls are ignored.

📝 Syntax

General form of deferred.notify:

deferred.notify( [ args ] )

Parameters

• args — optional values forwarded to every progress() callback (message string, percent number, status object, etc.).

Return value

• Returns the same Deferred object for chaining further notify(), resolve(), or reject() calls.

Minimal progress flow

const dfd = $.Deferred();

dfd.progress(function (message) {
  console.log("Progress:", message);
});

dfd.done(function () {
  console.log("Finished!");
});

dfd.notify("Processing...");
dfd.resolve();

Examples Gallery

Each example demonstrates progress reporting with notify(). Use the Try-it links to run them interactively.

const dfd = $.Deferred();

dfd.progress(function (message) {
  console.log("Progress:", message);
});

dfd.done(function () {
  console.log("Operation completed successfully!");
});

dfd.notify("Processing...");
dfd.resolve();

Progress: Processing...
Operation completed successfully!

const dfd = $.Deferred();
const steps = [25, 50, 75, 100];

dfd.progress(function (percent) {
  console.log("Upload:", percent + "%");
});

dfd.done(function () {
  console.log("Upload complete");
});

steps.forEach(function (pct) {
  dfd.notify(pct);
});

dfd.resolve({ file: "report.pdf" });

Upload: 25%
Upload: 50%
Upload: 75%
Upload: 100%
Upload complete

const dfd = $.Deferred();

dfd.progress(function (step) {
  console.log("Log step:", step);
});

dfd.progress(function (step) {
  $("#status").text("Step " + step + " of 3");
});

dfd.notify(1);
dfd.notify(2);
dfd.notify(3);
dfd.resolve("All steps done");

Log step: 1
Log step: 2
Log step: 3
(UI shows Step 3 of 3)

const dfd = $.Deferred();

dfd.progress(function (step, label, total) {
  console.log("Step " + step + "/" + total + ":", label);
});

dfd.notify(1, "Validate input", 3);
dfd.notify(2, "Process records", 3);
dfd.notify(3, "Save results", 3);
dfd.resolve();

Step 1/3: Validate input
Step 2/3: Process records
Step 3/3: Save results

const dfd = $.Deferred();

dfd.progress(function (msg) {
  console.log(msg);
});

dfd.done(function () {
  console.log("Operation completed successfully!");
});

setTimeout(function () {
  dfd.notify("Loading data...");
}, 400);

setTimeout(function () {
  dfd.notify("Processing...");
  dfd.resolve();
}, 1200);

Loading data...
Processing...
Operation completed successfully!

🚀 Use Cases

• File uploads — report bytes sent or percentage complete before the server confirms success.
• AJAX batch jobs — notify after each chunk loads while the overall request stays pending.
• Multi-step wizards — mark individual steps complete without resolving the whole flow.
• Long computations — share iteration counts or estimated time remaining during heavy client-side work.
• Progress bars and spinners — drive UI feedback from progress() while keeping final rendering in done().

📝 Notes

• notify() does not trigger done() or fail() — only progress() handlers.
• Call notify() only while the Deferred is pending; ignored after resolve/reject.
• Consumers reading a promise() view cannot call notify() — only the Deferred owner should emit progress.
• For custom this context in progress handlers, use notifyWith() (covered in the next tutorial).
• Native Promises have no progress API — this pattern is specific to jQuery Deferred.

💡 Best Practices