Time And Timers

Time and Timers

Clock plugin, TimerEvent, delays, loops, Timeline event sequencing, pausing time, time scale, and delta time in Phaser 4.

Key source paths: src/time/Clock.js, src/time/TimerEvent.js, src/time/Timeline.js, src/time/typedefs/, src/time/events/ Related skills: ../scenes/SKILL.md, ../tweens/SKILL.md

Quick Start

// In a Scene's create() method:

// One-shot delayed call (fires once after 1 second)
this.time.delayedCall(1000, () => {
    console.log('One second later');
});

// Repeating timer (fires 5 times, once every 500ms)
this.time.addEvent({
    delay: 500,
    callback: () => { console.log('tick'); },
    repeat: 4   // 4 repeats = 5 total fires
});

// Infinite loop timer
this.time.addEvent({
    delay: 1000,
    callback: this.spawnEnemy,
    callbackScope: this,
    loop: true
});

this.time is the scene's Clock instance (registered as the 'Clock' plugin under the key time). It creates and manages TimerEvent objects that fire callbacks based on game time.

Core Concepts

Clock (this.time)

The Clock is a Scene-level plugin that tracks game time and updates all of its TimerEvents each frame. Key properties:

• now -- current time in ms (equivalent to time passed to the scene update method).
• startTime -- timestamp when the scene started.
• timeScale -- multiplier applied to delta time. Default 1. Values above 1 speed up all timers; below 1 slow them down; 0 freezes time.
• paused -- when true, no TimerEvents are updated.

The Clock listens to PRE_UPDATE (to flush pending additions/removals) and UPDATE (to tick active events). It is automatically shut down and destroyed with the scene.

TimerEvent

A TimerEvent accumulates elapsed time each frame: elapsed += delta * clock.timeScale * event.timeScale. When elapsed >= delay, the callback fires. After all repeats are exhausted the event is removed from the Clock on the next frame.

Key properties set via config: delay, repeat, loop, callback, callbackScope, args, timeScale, startAt, paused.

Timeline (this.add.timeline)

A Timeline is a sequencer for scheduling actions at specific points in time. Unlike the Clock (which manages independent timers), a Timeline runs a linear sequence of events keyed by absolute or relative timestamps.

const timeline = this.add.timeline([
    { at: 0,    run: () => { /* immediate */ } },
    { at: 1000, run: () => { /* at 1s */ } },
    { at: 2500, tween: { targets: sprite, alpha: 0, duration: 500 } }
]);
timeline.play();

Timelines always start paused. You must call play() to start them. They are created via the GameObjectFactory and destroyed automatically when the scene shuts down.

Common Patterns

Delayed Call

// Shorthand -- fires once, no repeat
this.time.delayedCall(2000, () => {
    this.scene.start('GameOver');
});

Repeating Timer with Finite Count

// repeat: 9 means 10 total fires (1 initial + 9 repeats)
const timer = this.time.addEvent({
    delay: 200,
    callback: this.fireBullet,
    callbackScope: this,
    repeat: 9
});

// Check progress
timer.getRepeatCount();       // repeats remaining
timer.getOverallProgress();   // 0..1 across all repeats

Infinite Loop

const spawner = this.time.addEvent({
    delay: 3000,
    callback: this.spawnWave,
    callbackScope: this,
    loop: true
});

// Stop it later
spawner.remove();  // or spawner.paused = true to pause

Setting repeat: -1 is equivalent to loop: true.

First-Fire Shortcut with startAt

// First fire happens quickly (after 100ms), then every 2s
this.time.addEvent({
    delay: 2000,
    callback: this.heartbeat,
    callbackScope: this,
    loop: true,
    startAt: 1900  // pre-fill elapsed so first fire is at 100ms
});

Stopping and Removing Timers

const timer = this.time.addEvent({ delay: 1000, loop: true, callback: fn });

// Option 1: Remove from clock (schedules removal next frame)
timer.remove();            // silently expires
timer.remove(true);        // fires callback one last time, then expires

// Option 2: Remove via Clock
this.time.removeEvent(timer);

// Option 3: Remove all timers
this.time.removeAllEvents();

Pausing and Resuming

// Pause the entire Clock (all timers freeze)
this.time.paused = true;
this.time.paused = false;

// Pause a single timer
timer.paused = true;
timer.paused = false;

Time Scale (Slow Motion / Fast Forward)

// Slow all timers in this scene to half speed
this.time.timeScale = 0.5;

// Speed up a single timer to 2x
timer.timeScale = 2;

// Combined: effective scale = clock.timeScale * event.timeScale
// So 0.5 * 2 = 1x for that specific timer

Reading Timer State

timer.getProgress();              // 0..1 for current iteration
timer.getOverallProgress();       // 0..1 across all repeats
timer.getElapsed();               // ms elapsed this iteration
timer.getElapsedSeconds();        // seconds elapsed this iteration
timer.getRemaining();             // ms until next fire
timer.getRemainingSeconds();      // seconds until next fire
timer.getOverallRemaining();      // ms until final fire
timer.getOverallRemainingSeconds(); // seconds until final fire
timer.getRepeatCount();           // repeats left

Timeline: Sequencing Events

const timeline = this.add.timeline([
    {
        at: 0,
        run: () => { this.title.setAlpha(1); },
        sound: 'intro'
    },
    {
        at: 2000,
        tween: { targets: this.title, y: 100, duration: 1000 },
        sound: { key: 'whoosh', config: { volume: 0.5 } }
    },
    {
        at: 4000,
        set: { alpha: 0 },
        target: this.title,
        event: 'INTRO_DONE'
    }
]);

timeline.on('INTRO_DONE', (target) => { /* custom event */ });
timeline.on('complete', (tl) => { /* all events ran */ });
timeline.play();

Timeline: Relative Timing with from and in

const timeline = this.add.timeline([
    { at: 1000, run: stepOne },         // absolute: 1s from start
    { from: 500, run: stepTwo },        // relative: 500ms after previous (1.5s)
    { from: 1000, run: stepThree }      // relative: 1000ms after previous (2.5s)
]);

• at -- absolute ms from timeline start (default 0).
• in -- offset from current elapsed time (useful when adding events to a running timeline).
• from -- offset from the previous event's start time.

Priority: from overrides in, which overrides at.

Timeline: Conditional Events

const timeline = this.add.timeline([
    {
        at: 5000,
        if: () => this.player.health > 0,
        run: () => { this.showBonusRound(); }
    }
]);

If the if callback returns false, the event is skipped (marked complete but actions are not executed).

Timeline: Looping

const timeline = this.add.timeline([
    { at: 0, run: () => console.log('start') },
    { at: 1000, run: () => console.log('end') }
]);

timeline.repeat().play();      // infinite loop
timeline.repeat(3).play();     // loop 3 additional times (4 total runs)
timeline.repeat(false).play(); // no looping

The loop callback on a TimelineEventConfig fires on repeat iterations (not the first run).

Timeline: Pause, Resume, Stop, Reset

timeline.pause();      // freezes elapsed counter and pauses spawned tweens
timeline.resume();     // resumes elapsed counter and unpauses spawned tweens
timeline.stop();       // sets paused=true, complete=true
timeline.reset();      // elapsed=0, all events marked incomplete, starts playing
timeline.isPlaying();  // true if not paused and not complete
timeline.getProgress(); // 0..1 based on events completed / total events

Timeline: Time Scale

timeline.timeScale = 2;   // double speed
timeline.timeScale = 0.5; // half speed

Note: Timeline timeScale does not affect tweens created by the timeline. Set tween timeScale separately.

Timeline: Full Cutscene Example

Timelines excel at choreographing cutscenes with mixed actions (callbacks, tweens, sounds, property sets, and custom events):

class CutsceneScene extends Phaser.Scene {
    create() {
        const timeline = this.add.timeline([
            {
                at: 0,
                run: () => { console.log('Start!'); }
            },
            {
                at: 1000,
                tween: {
                    targets: this.player,
                    x: 400,
                    duration: 500,
                    ease: 'Power2'
                }
            },
            {
                at: 1500,
                sound: 'doorOpen'
            },
            {
                at: 2000,
                set: { visible: true },
                target: this.door
            },
            {
                from: 500,
                run: () => { console.log('Relative timing'); }
            },
            {
                at: 5000,
                event: 'cutsceneDone',
                stop: true
            }
        ]);

        timeline.on('cutsceneDone', () => {
            this.scene.start('GameScene');
        });

        timeline.play();
    }
}

Timer Reset and Reuse

A completed TimerEvent can be reset with a new config and re-added to the Clock:

const timer = this.time.addEvent({
    delay: 1000,
    callback: this.phase1,
    callbackScope: this,
    repeat: 2
});

// Later, after it completes, reconfigure and re-add:
timer.reset({
    delay: 500,
    callback: this.phase2,
    callbackScope: this,
    repeat: 4
});
this.time.addEvent(timer);  // must re-add; reset() alone does not schedule it

Configuration Reference

TimerEventConfig

TimelineEventConfig

TimelineEvent (Internal)

The processed event object stored in timeline.events[]. Extends config with:

Events

Timeline Events

Custom events via the event property in TimelineEventConfig are also emitted on the Timeline instance with signature (target).

TimerEvent / Clock

TimerEvent and Clock do not emit EventEmitter events. Timers use the callback property directly. The Clock is managed by scene lifecycle events (PRE_UPDATE, UPDATE, SHUTDOWN, DESTROY).

API Quick Reference

Clock (this.time)

TimerEvent

Timeline (this.add.timeline)

Gotchas

1. repeat vs total fires. repeat: 4 means 5 total callback invocations (1 initial + 4 repeats). This is a common off-by-one source.
2. Zero delay with repeat throws. A TimerEvent with delay: 0 and any repeat/loop will throw 'TimerEvent infinite loop created via zero delay'.
3. Timelines start paused. You must call timeline.play() after creation. Forgetting this is a frequent mistake.
4. Timeline timeScale does not affect tweens. Setting timeline.timeScale only scales the timeline's own elapsed counter. Tweens created by the timeline run at their own speed. Set tween timeScale separately or use the TweenManager.
5. once events are removed permanently. Timeline events with once: true are spliced out after firing and will not reappear on reset() or when looping.
6. Timer additions are deferred. addEvent() pushes to a pending list processed in preUpdate. The timer will not be active until the next frame.
7. Clock paused vs timeScale 0. Both freeze timers, but paused = true skips the update loop entirely, while timeScale = 0 still runs the loop with zero delta. Prefer paused for a full freeze.
8. callbackScope default. If you omit callbackScope, the TimerEvent itself becomes this inside the callback, not the scene. Use arrow functions or pass callbackScope: this explicitly.
9. Reusing TimerEvent instances. You can pass a TimerEvent object to addEvent(), but it must not be in a completed state. The Clock will reset its elapsed and dispatch state.
10. Timeline from chains. Each from offset is relative to the previous event's resolved time, not the previous from value. Events are processed in array order.
11. Scene pause pauses the Timeline. When a scene is paused (scene.pause()), the Timeline's update loop stops too, since Timeline updates are driven by the scene's update step.
12. timer.reset() does not re-add to Clock. Calling timer.reset(config) reinitializes the timer but does not schedule it. You must call this.time.addEvent(timer) again after resetting.

Source File Map