kute.js/src/interpolation/rotate3d.js

/**
 * 3D Rotation Interpolation Function.
 *
 * @param {number} a start [x,y,z] angles
 * @param {number} b end [x,y,z] angles
 * @param {string} u unit, usually `deg` degrees
 * @param {number} v progress
 * @returns {string} the interpolated 3D rotation string
 */
export default function rotate3d(a, b, u, v) {
  let rotateStr = '';
  // eslint-disable-next-line no-bitwise
  rotateStr += a[0] || b[0] ? `rotateX(${((a[0] + (b[0] - a[0]) * v) * 1000 >> 0) / 1000}${u})` : '';
  // eslint-disable-next-line no-bitwise
  rotateStr += a[1] || b[1] ? `rotateY(${((a[1] + (b[1] - a[1]) * v) * 1000 >> 0) / 1000}${u})` : '';
  // eslint-disable-next-line no-bitwise
  rotateStr += a[2] || b[2] ? `rotateZ(${((a[2] + (b[2] - a[2]) * v) * 1000 >> 0) / 1000}${u})` : '';
  return rotateStr;
}