Function loop

Libraries/Animated/src/AnimatedImplementation.js:2293–2342

(
  animation: CompositeAnimation,
  { iterations = -1 }: LoopAnimationConfig = {},
)

type LoopAnimationConfig = { iterations: number };

var loop = function(
  animation: CompositeAnimation,
  { iterations = -1 }: LoopAnimationConfig = {},
): CompositeAnimation {
  var isFinished = false;
  var iterationsSoFar = 0;
  return {
    start: function(callback?: ?EndCallback) {
      var restart = function(result: EndResult = {finished: true}): void {
        if (isFinished ||
            (iterationsSoFar === iterations) ||
            (result.finished === false)) {
          callback && callback(result);
        } else {
          iterationsSoFar++;
          animation.reset();
          animation.start(restart);
        }
      };
      if (!animation || iterations === 0) {
        callback && callback({finished: true});
      } else {
        if (animation._isUsingNativeDriver()) {
          animation._startNativeLoop(iterations);
        } else {
          restart(); // Start looping recursively on the js thread
        }
      }
    },

    stop: function(): void {
      isFinished = true;
      animation.stop();
    },

    reset: function(): void {
      iterationsSoFar = 0;
      isFinished = false;
      animation.reset();
    },

    _startNativeLoop: function() {
      throw new Error('Loops run using the native driver cannot contain Animated.loop animations');
    },

    _isUsingNativeDriver: function(): boolean {
      return animation._isUsingNativeDriver();
    }
  };
};

type Mapping = {[key: string]: Mapping} | AnimatedValue;
type EventConfig = {