Method constructor

src/gsap-core.js:2322–2418

(targets, vars, position, skipInherit)

export class Tween extends Animation {

	constructor(targets, vars, position, skipInherit) {
		if (typeof(vars) === "number") {
			position.duration = vars;
			vars = position;
			position = null;
		}
		super(skipInherit ? vars : _inheritDefaults(vars));
		let { duration, delay, immediateRender, stagger, overwrite, keyframes, defaults, scrollTrigger } = this.vars,
			parent = vars.parent || _globalTimeline,
			parsedTargets = (_isArray(targets) || _isTypedArray(targets) ? _isNumber(targets[0]) : ("length" in vars)) ? [targets] : toArray(targets), // edge case: someone might try animating the "length" of an object with a "length" property that's initially set to 0 so don't interpret that as an empty Array-like object.
			tl, i, copy, l, p, curTarget, staggerFunc, staggerVarsToMerge;
		this._targets = parsedTargets.length ? _harness(parsedTargets) : _warn("GSAP target " + targets + " not found. https://gsap.com", !_config.nullTargetWarn) || [];
		this._ptLookup = []; //PropTween lookup. An array containing an object for each target, having keys for each tweening property
		this._overwrite = overwrite;
		if (keyframes || stagger || _isFuncOrString(duration) || _isFuncOrString(delay)) {
			vars = this.vars;
			let easeReverse = vars.easeReverse || vars.yoyoEase;
			tl = this.timeline = new Timeline({data: "nested", defaults: defaults || {}, targets: parent && parent.data === "nested" ? parent.vars.targets : parsedTargets}); // we need to store the targets because for staggers and keyframes, we end up creating an individual tween for each but function-based values need to know the index and the whole Array of targets.
			tl.kill();
			tl.parent = tl._dp = this;
			tl._start = 0;
			if (stagger || _isFuncOrString(duration) || _isFuncOrString(delay)) {
				l = parsedTargets.length;
				staggerFunc = stagger && distribute(stagger);
				if (_isObject(stagger)) { //users can pass in callbacks like onStart/onComplete in the stagger object. These should fire with each individual tween.
					for (p in stagger) {
						if (~_staggerTweenProps.indexOf(p)) {
							staggerVarsToMerge || (staggerVarsToMerge = {});
							staggerVarsToMerge[p] = stagger[p];
						}
					}
				}
				for (i = 0; i < l; i++) {
					copy = _copyExcluding(vars, _staggerPropsToSkip);
					copy.stagger = 0;
					easeReverse && (copy.easeReverse = easeReverse);
					staggerVarsToMerge && _merge(copy, staggerVarsToMerge);
					curTarget = parsedTargets[i];
					//don't just copy duration or delay because if they're a string or function, we'd end up in an infinite loop because _isFuncOrString() would evaluate as true in the child tweens, entering this loop, etc. So we parse the value straight from vars and default to 0.
					copy.duration = +_parseFuncOrString(duration, this, i, curTarget, parsedTargets);
					copy.delay = (+_parseFuncOrString(delay, this, i, curTarget, parsedTargets) || 0) - this._delay;
					if (!stagger && l === 1 && copy.delay) { // if someone does delay:"random(1, 5)", repeat:-1, for example, the delay shouldn't be inside the repeat.
						this._delay = delay = copy.delay;
						this._start += delay;
						copy.delay = 0;
					}
					tl.to(curTarget, copy, staggerFunc ? staggerFunc(i, curTarget, parsedTargets) : 0);
					tl._ease = _easeMap.none;
				}
				tl.duration() ? (duration = delay = 0) : (this.timeline = 0); // if the timeline's duration is 0, we don't need a timeline internally!
			} else if (keyframes) {
				_inheritDefaults(_setDefaults(tl.vars.defaults, {ease:"none"}));
				tl._ease = _parseEase(keyframes.ease || vars.ease || "none");
				let time = 0,
					a, kf, v;
				if (_isArray(keyframes)) {
					keyframes.forEach(frame => tl.to(parsedTargets, frame, ">"));
					tl.duration(); // to ensure tl._dur is cached because we tap into it for performance purposes in the render() method.