経過時間ごとに関数を発火させるタイムライン関数

timeline.js

// # arg
// sequence: array
// [
//  { time: number, exec: function },
//  { time: number, exec: function },
//  ...
// ]
//
// # usage
// const sampleTimeline = timeline(sequence);
// sampleTimeline.exec(time);
//
// TOOD: sequenceはcopyしてからsortする
//
export default function timeline(sequence) {
  sequence.sort((a, b) => {
    if (a.time < b.time) return -1
    if (a.time > b.time) return 1
    return 0
  })
  const exec = t => {
    // guard
    if (sequence.length < 1) return

    let spliceIndex = 0
    for (let i = 0; i < sequence.length; i++) {
      const { time } = sequence[i]
      if (t > time) spliceIndex = i + 1
    }

    // no target
    if (spliceIndex < 1) {
      return
    }

    const executionTargets = sequence.splice(0, spliceIndex)
    for (let i = 0; i < executionTargets.length; i++) {
      executionTargets[i].exec(t)
    }
  }

  return {
    exec,
  }
}