@phaserjs/phaser/math/easing/bounce/InOut.js

Phaser 4

export function InOut(v) {
  let reverse = false;
  if (v < 0.5) {
    v = 1 - v * 2;
    reverse = true;
  } else {
    v = v * 2 - 1;
  }
  if (v < 1 / 2.75) {
    v = 7.5625 * v * v;
  } else if (v < 2 / 2.75) {
    v = 7.5625 * (v -= 1.5 / 2.75) * v + 0.75;
  } else if (v < 2.5 / 2.75) {
    v = 7.5625 * (v -= 2.25 / 2.75) * v + 0.9375;
  } else {
    v = 7.5625 * (v -= 2.625 / 2.75) * v + 0.984375;
  }
  if (reverse) {
    return (1 - v) * 0.5;
  } else {
    return v * 0.5 + 0.5;
  }
}