Guides · 06

Timelines

Run many tracks from one seekable clock: play, pause, seek, reverse and change the rate.

Tracks on one clock

useTimeline(tracks, options, deps) creates a timeline owned by the component. Each track is a list of keyframes, or { values, times, at, duration } with at and duration in milliseconds.

progress is one CSS variable, and numeric or length tracks are calc() expressions of it, so a timeline in ordinary style writes one variable per frame.

Preparing the example…

JavaScript is off. The code below is the complete example.

App.jsx

import { useRef } from 'react';
import { useTimeline } from '@kkwaenggwari/animated';
import './styles.css';

export default function App({ duration = 3000, repeat = true }) {
  const timeline = useTimeline(
    {
      x: ['0px', '220px', '220px', '0px', '0px'],
      y: ['0px', '0px', '110px', '110px', '0px'],
      turn: ['0deg', '90deg', '180deg', '270deg', '360deg'],
      round: ['50%', '12%', '50%', '12%', '50%'],
    },
    { duration, repeat: repeat ? Infinity : 0 },
    [duration, repeat],
  );
  const bar = useRef(null);

  const seek = (event) => {
    const box = bar.current.getBoundingClientRect();
    const ratio = Math.min(1, Math.max(0, (event.clientX - box.left) / box.width));
    timeline.pause();
    timeline.seek(ratio * timeline.duration);
  };

  const { x, y, turn, round } = timeline.values;

  return (
    <div className="stage">
      <div className="canvas">
        <span
          className="shape"
          style={{ transform: `translate(${x}, ${y}) rotate(${turn})`, borderRadius: round }}
        />
      </div>
      <div className="player">
        <button type="button" onClick={() => timeline.play()}>
          Play
        </button>
        <button type="button" onClick={() => timeline.pause()}>
          Pause
        </button>
        <div
          ref={bar}
          className="scrub"
          onPointerDown={(event) => {
            event.currentTarget.setPointerCapture(event.pointerId);
            seek(event);
          }}
          onPointerMove={(event) => {
            if (event.buttons) seek(event);
          }}
        >
          <span style={{ transform: `scaleX(${timeline.progress})` }} />
        </div>
      </div>
    </div>
  );
}

styles.css

.stage {
  display: grid;
  gap: 16px;
  padding: 28px;
}

.canvas {
  height: 190px;
  padding: 20px;
  border-radius: 16px;
  background: #0b1440;
}

.shape {
  display: block;
  width: 60px;
  height: 60px;
  background: #5c7cff;
}

.player {
  display: flex;
  align-items: center;
  gap: 8px;
}

.player button {
  min-height: 40px;
  padding: 0 16px;
  border: 1px solid #e4e6ef;
  border-radius: 999px;
  background: #fff;
  font: inherit;
  cursor: pointer;
}

.scrub {
  flex: 1;
  height: 12px;
  border-radius: 999px;
  background: #eef2ff;
  overflow: hidden;
  cursor: pointer;
  touch-action: none;
}

.scrub span {
  display: block;
  height: 100%;
  background: #2854ff;
  transform-origin: left center;
}

Playback control

play({ from, rate }), pause(), seek(ms) and reverse() control the clock. state, currentTime, duration and the finished promise describe it. repeat and repeatDelay loop it.

Title.jsx

const intro = useTimeline(
  {
    y: ['24px', '0px'],
    fade: { values: [0, 1], at: 0, duration: 300 },
    line: { values: [0, 1], at: 200, duration: 600 },
  },
  { duration: 800 },
);

intro.seek(400); // milliseconds
intro.play({ rate: 0.5 });
intro.reverse();

Outside React

createTimeline is the same clock without a component. Call dispose() when you are done.