gsap/src/CustomBounce.js

GSAP is a framework-agnostic JavaScript animation library that turns developers into animation superheroes. Build high-performance animations that work in **every** major browser. Animate CSS, SVG, canvas, React, Vue, WebGL, colors, strings, motion paths,

/*!
 * CustomBounce 3.13.0
 * https://gsap.com
 *
 * @license Copyright 2008-2025, GreenSock. All rights reserved.
 * Subject to the terms at https://gsap.com/standard-license
 * @author: Jack Doyle, jack@greensock.com
*/
/* eslint-disable */

let gsap, _coreInitted, createCustomEase,
	_getGSAP = () => gsap || (typeof(window) !== "undefined" && (gsap = window.gsap) && gsap.registerPlugin && gsap),
	_initCore = required => {
		gsap = _getGSAP();
		createCustomEase = gsap && gsap.parseEase("_CE");
		if (createCustomEase) {
			_coreInitted = 1;
			gsap.parseEase("bounce").config = vars => typeof(vars) === "object" ? _create("", vars) : _create("bounce(" + vars + ")", {strength:+vars});
		} else {
			required && console.warn("Please gsap.registerPlugin(CustomEase, CustomBounce)");
		}
	},
	_normalizeX = a => { //scales all the x values in an array [x, y, x, y...] AND rounds them to the closest hundredth (decimal)
		let l = a.length,
			s = 1 / a[l - 2],
			rnd = 1000,
			i;
		for (i = 2; i < l; i += 2) {
			a[i] = ~~(a[i] * s * rnd) / rnd;
		}
		a[l - 2] = 1; //in case there are any rounding errors. x should always end at 1.
	},
	_bonusValidated = 1, //<name>CustomBounce</name>
	_create = (id, vars) => {
		if (!_coreInitted) {
			_initCore(1);
		}
		vars = vars || {};
		if (_bonusValidated) {
			let max = 0.999,
				decay = Math.min(max, vars.strength || 0.7),  // Math.min(0.999, 1 - 0.3 / (vars.strength || 1)),
				decayX = decay,
				gap = (vars.squash || 0) / 100,
				originalGap = gap,
				slope = 1 / 0.03,
				w = 0.2,
				h = 1,
				prevX = 0.1,
				path = [0, 0, 0.07, 0, 0.1, 1, 0.1, 1],
				squashPath = [0, 0, 0, 0, 0.1, 0, 0.1, 0],
				cp1, cp2, x, y, i, nextX, squishMagnitude;
			for (i = 0; i < 200; i++) {
				w *= decayX * ((decayX + 1) / 2);
				h *= decay * decay;
				nextX = prevX + w;
				x = prevX + w * 0.49;
				y = 1 - h;
				cp1 = prevX + h / slope;
				cp2 = x + (x - cp1) * 0.8;

				if (gap) {
					prevX += gap;
					cp1 += gap;
					x += gap;
					cp2 += gap;
					nextX += gap;
					squishMagnitude = gap / originalGap;
					squashPath.push(
						prevX - gap, 0,
						prevX - gap, squishMagnitude,
						prevX - gap / 2, squishMagnitude, //center peak anchor
						prevX, squishMagnitude,
						prevX, 0,
						prevX, 0, //base anchor
						prevX, squishMagnitude * -0.6,
						prevX + (nextX - prevX) / 6, 0,
						nextX, 0
					);
					path.push(prevX - gap, 1,
						prevX, 1,
						prevX, 1);
					gap *= decay * decay;
				}

				path.push(prevX, 1,
					cp1, y,
					x, y,
					cp2, y,
					nextX, 1,
					nextX, 1);

				decay *= 0.95;
				slope = h / (nextX - cp2);
				prevX = nextX;
				if (y > max) {
					break;
				}
			}

			if (vars.endAtStart && vars.endAtStart !== "false") {
				x = -0.1;
				path.unshift(x, 1, x, 1, -0.07, 0);
				if (originalGap) {
					gap = originalGap * 2.5; //make the initial anticipation squash longer (more realistic)
					x -= gap;
					path.unshift(x, 1, x, 1, x, 1);
					squashPath.splice(0, 6);
					squashPath.unshift(x, 0, x, 0, x, 1, x + gap / 2, 1, x + gap, 1, x + gap, 0, x + gap, 0, x + gap, -0.6, x + gap + 0.033, 0);
					for (i = 0; i < squashPath.length; i+=2) {
						squashPath[i] -= x;
					}
				}
				for (i = 0; i < path.length; i+=2) {
					path[i] -= x;
					path[i+1] = 1 - path[i+1];
				}
			}
			if (gap) {
				_normalizeX(squashPath);
				squashPath[2] = "C" + squashPath[2];
				createCustomEase(vars.squashID || (id + "-squash"), "M" + squashPath.join(","));
			}
			_normalizeX(path);
			path[2] = "C" + path[2];
			return createCustomEase(id, "M" + path.join(","));
		}
	};

export class CustomBounce {

	constructor(id, vars) {
		this.ease = _create(id, vars);
	}

	static create(id, vars) {
		return _create(id, vars);
	}

	static register(core) {
		gsap = core;
		_initCore();
	}

}

_getGSAP() && gsap.registerPlugin(CustomBounce);

CustomBounce.version = "3.13.0";

export { CustomBounce as default };