scene.js - basic Timeline-driven animation functions

scene.js

export const progress = (t, start, end) =>
  t < start ? 0 :
  t > end ? 1 :
  (t / (end - start));

export const tween = (start, end, step, state, t) =>
  step(state, progress(t, start, end));

export const event = (time, step, state, t) =>
  t < time ? step(state, 0) : step(state, 1);

export const scene = callback => duration => {
  const start = performance.now();

  const frame = (t) => {
    const elapsed = (t - start);
    callback(elapsed);
    if (elapsed < duration) requestAnimationFrame(frame);
  };

  requestAnimationFrame(frame);
};