jQuery callbacks.fire() Method — Invoke Handlers

What Is fire()?

callbacks.fire(arguments) runs every handler on a jQuery Callbacks list (since jQuery 1.7), in add order, with the arguments you pass. It returns the same Callbacks object for chaining.

callbacks.add(foo)
callbacks.fire("hello")   // foo("hello")
callbacks.fire("world")   // foo("world") again

add()  → queue handlers
fire() → run them now

returns the Callbacks object (chainable)

How to Use fire()

Build a list, add handlers, then fire when the event or step is ready.

1. Create a list with $.Callbacks() (optional flags such as once).
2. Register handlers with add(fn).
3. Call fire(arg1, arg2, …) to run every handler with those args.
4. Call fire() again anytime (unless the list uses once or was disabled).

Pseudocode

function fire(callbacks, args...):
    if callbacks is disabled: return callbacks
    if once and already fired: return callbacks

    for each handler in callbacks.list (in order):
        handler(args...)
        if stopOnFalse and handler returned false: break

    mark list as fired
    return callbacks

Cheat Sheet

Keep these facts handy when publishing to a Callbacks list.

Live Preview

Fire a small Callbacks list and watch handler output accumulate.

Ready — pick an action and click Run.

jQuery Examples

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

var foo = function (value) {
  console.log("foo: " + value);
};

var callbacks = $.Callbacks();
callbacks.add(foo);

callbacks.fire("hello");  // foo: hello
callbacks.fire("world");  // foo: world

foo: hello
foo: world

var lines = [];
var foo = function (value) { lines.push("foo: " + value); };
var bar = function (value) { lines.push("bar: " + value); };

var callbacks = $.Callbacks();
callbacks.add(foo);
callbacks.add(bar);
callbacks.fire("hello again");

console.log(lines.join("\\n"));
// foo: hello again
// bar: hello again

foo: hello again
bar: hello again

var lines = [];
var cbs = $.Callbacks("once");
cbs.add(function (msg) { lines.push(msg); });

cbs.fire("first");
cbs.fire("second");  // ignored

console.log(lines.join(", "));  // "first"

first

var empty = $.Callbacks();
empty.fire("noop");  // no handlers — no error

var cbs = $.Callbacks();
cbs.add(function () { console.log("hi"); });
cbs.disable();
cbs.fire("x");       // no-op
console.log(cbs.disabled());  // true

empty fire: ok
disabled: true
(no "hi")

Performance Notes

*Unless the list uses unique. Prefer lean handlers — one slow callback delays every later subscriber in the same fire().

Key Takeaways