animejs/dist/modules/core/clock.js

JavaScript animation engine

/**
 * Anime.js - core - ESM
 * @version v4.3.6
 * @license MIT
 * @copyright 2026 - Julian Garnier
 */

import { K, maxFps, minValue, tickModes } from './consts.js';
import { defaults } from './globals.js';

/**
 * @import {
 *   Tickable,
 *   Tween,
 * } from '../types/index.js'
*/

/*
 * Base class to control framerate and playback rate.
 * Inherited by Engine, Timer, Animation and Timeline.
 */
class Clock {

  /** @param {Number} [initTime] */
  constructor(initTime = 0) {
    /** @type {Number} */
    this.deltaTime = 0;
    /** @type {Number} */
    this._currentTime = initTime;
    /** @type {Number} */
    this._lastTickTime = initTime;
    /** @type {Number} */
    this._startTime = initTime;
    /** @type {Number} */
    this._lastTime = initTime;
    /** @type {Number} */
    this._scheduledTime = 0;
    /** @type {Number} */
    this._frameDuration = K / maxFps;
    /** @type {Number} */
    this._fps = maxFps;
    /** @type {Number} */
    this._speed = 1;
    /** @type {Boolean} */
    this._hasChildren = false;
    /** @type {Tickable|Tween} */
    this._head = null;
    /** @type {Tickable|Tween} */
    this._tail = null;
  }

  get fps() {
    return this._fps;
  }

  set fps(frameRate) {
    const previousFrameDuration = this._frameDuration;
    const fr = +frameRate;
    const fps = fr < minValue ? minValue : fr;
    const frameDuration = K / fps;
    if (fps > defaults.frameRate) defaults.frameRate = fps;
    this._fps = fps;
    this._frameDuration = frameDuration;
    this._scheduledTime += frameDuration - previousFrameDuration;
  }

  get speed() {
    return this._speed;
  }

  set speed(playbackRate) {
    const pbr = +playbackRate;
    this._speed = pbr < minValue ? minValue : pbr;
  }

  /**
   * @param  {Number} time
   * @return {tickModes}
   */
  requestTick(time) {
    const scheduledTime = this._scheduledTime;
    this._lastTickTime = time;
    // If the current time is lower than the scheduled time
    // this means not enough time has passed to hit one frameDuration
    // so skip that frame
    if (time < scheduledTime) return tickModes.NONE;
    const frameDuration = this._frameDuration;
    const frameDelta = time - scheduledTime;
    // Ensures that _scheduledTime progresses in steps of at least 1 frameDuration.
    // Skips ahead if the actual elapsed time is higher.
    this._scheduledTime += frameDelta < frameDuration ? frameDuration : frameDelta;
    return tickModes.AUTO;
  }

  /**
   * @param  {Number} time
   * @return {Number}
   */
  computeDeltaTime(time) {
    const delta = time - this._lastTime;
    this.deltaTime = delta;
    this._lastTime = time;
    return delta;
  }

}

export { Clock };