SearchBarAnimation.js

_handleIntermediateState = (scrollToOffset) => {
  let scrollY = this.scrollY._value;
  if(scrollY < this.topPartHeight) { // Full
    scrollToOffset(scrollY > (this.topPartHeight / 2) ? this.topPartHeight : 0);
  } else { // Clamped
    if(
      this._clampedScrollValue < this.maxClamp && 
      this._clampedScrollValue > this.minClamp
    ) {
      let scrollTo;
      if(this._clampedScrollValue > (this.maxClamp + this.minClamp) / 2) {
        scrollTo = scrollY + this._interpolate(
          this._clampedScrollValue, 
          [this.maxClamp, this.minClamp], 
          [0, this.diffClamp]
        );
      } else {
        scrollTo = scrollY - this._interpolate(
          this._clampedScrollValue, 
          [this.minClamp, this.maxClamp], 
          [0, this.diffClamp]
        );
      }

      scrollToOffset(scrollTo);
    }
  }
}

_interpolate = (x, inputRange, outputRange) => {
  let minX = inputRange[0];
  let maxX = inputRange[1];
  let minY = outputRange[0];
  let maxY = outputRange[1];

  return (x - minX) * ((maxY - minY) / (maxX - minX) + minY);
}