Tweeny Weeny 🤏

A weeeally tweeny simple tweening library based on EventEmitter3.

Features:

• Full set of easing functions available (including linear)
• Stop a tween during execution
• "start", "stop", "update", "complete" events available for full lifecycle awareness using EventEmitter3 API
• Re-usable Tween instances. Instance keeps last known value persistent and can be re-started

Works in the Browser or Node. For the browser requestAnimationFrame is used, where as in Node setTimeout(0) is used. Frames are generated at the fastest rate available over the desired duration.

Install

Install as dependency through npm.

npm install tweenyweeny

Usage

Simply create a new Tween object (optionally passing the desired duration in milliseconds, default is 150ms).

import { Tween } from "tweenyweeny";

const FROM = 10;
const TO = 20;
const DURATION = 1000; // 1 second
const EASE_FUNCTION = "easeOutQuad";

/* create an instance of Tween, re-use for future animations on same property if required */
const tween = new Tween(DURATION);

/* listen for updates */
tween.on("update", (currentValue) => {
  myThing.theProp = currentValue;
});

tween.on("complete", () => {
  /* animation done */
});

/* start animation */
tween.start(FROM, TO, EASE_FUNCTION);

/* or use the static method */
Tween.run(
  (currentValue) => {
    myThing.theProp = currentValue;
  },
  FROM,
  TO,
  DURATION,
  EASE_FUNCTION
);

Instance API

A Tween is an EventEmitter3 object, so all of that API is available to listen to events.

Member	Parameters	Return Value	Description
new Tween([duration])	* (optional) duration: number - The animation duration in milliseconds (defaults to 150ms)	Tween	Create a new instance of Tweenwith the optional duration in milliseconds.
.start(from, to[, easing])	* from: number - The initial value to start the animation from * to: number - The value to end the animation with * (optional) easing: EasingFunctionName - The name of the easing function to use (defaults to easeOutQuad)	Promise<void>	Start the animation interpolating between the from and to values using the optional easing function name, return a promise. You can also bind to the complete event to be notified when done.
.stop()		void	Stop the animation at the current value.
.onStart(callback)	* callback: () => void - The callback to bind the start event to	Tween	Shortcut for .on('start', callback) to bind a callback to the start event.
.onUpdate(callback)	* callback: () => void - The callback to bind the update event to	Tween	Shortcut for .on('update', callback) to bind a callback to the update event.
.onStop(callback)	* callback: () => void - The callback to bind the stop event to	Tween	Shortcut for .on('stop', callback) to bind a callback to the stop event.
.onComplete(callback)	* callback: () => void - The callback to bind the complete event to	Tween	Shortcut for .on('complete', callback) to bind a callback to the complete event.
.isRunning		boolean	Whether the tween is currently running
.currentValue		number	The last computed value for the tween. This will persist after the animation completes.

Events

Event	Callback	Description
"start"	(from: number, to: number) => void	Fired when the Tween is started with .start(). Passes the from and to values if needed.
"update"	(currentValue: number) => void	Fired during each frame of the Tween during animation. Passes the current value.
"stop"	(currentValue: number) => void	Fired when the Tween is stopped with .stop() or when .start() is called while a tween is running. Passes the current value value if needed.
"complete"	(from: number, to: number) => void	Fired when the animation completes after calling .start(). Passes the from and to values if needed.

Static API

Member	Parameters	Return Value	Description
Tween.run(callback, from, to[, duration, [easing]])	* callback: (value: number) => void - The update function to call each frame with the current value * from: number - The initial value to start the animation from * to: number - The value to end the animation with * (optional) duration: number - The duration in milliseconds * (optional) easing: EasingFunctionName - The name of the easing function to use (defaults to "easeOutQuad")	Promise<void>	Create a new Tween with the given settings and start the animation, returning a promise.
Tween.defaultDurationMs		number	The default duration to use for new instances.

Easing Function Names

The following easing function names are available (see https://easings.net for demos):

• "linear"
• "easeInSine"
• "easeOutSine"
• "easeInOutSine"
• "easeInQuad"
• "easeOutQuad" (default)
• "easeInOutQuad"
• "easeInCubic"
• "easeOutCubic"
• "easeInOutCubic"
• "easeInQuart"
• "easeOutQuart"
• "easeInOutQuart"
• "easeInQuint"
• "easeOutQuint"
• "easeInOutQuint"
• "easeInExpo"
• "easeOutExpo"
• "easeInOutExpo"
• "easeInCirc"
• "easeOutCirc"
• "easeInOutCirc"
• "easeInBack"
• "easeOutBack"
• "easeInOutBack"
• "easeInElastic"
• "easeOutElastic"
• "easeInOutElastic"
• "easeInBounce"
• "easeOutBounce"
• "easeInOutBounce"

Issues

Please report any issues, feedback, bugs or suggestions here.