animateWithClosure.js

// In the initial code, I wasn't aware that let would create a new binding for 
// each variable inside my loop. I assumed a closure around the setTimeout function
// was necessary to create new copy of the variables at each step.
animate() {
  let previousDelay = 0;
  let styles = null;
  for (let sequence of this.dataSet) {
    let delay = sequence[0] + previousDelay;
    let objects = sequence.filter(this.isObject);
    styles = this.formatStyles(objects);
    this.handleTimer(delay, styles);
    previousDelay = delay;
  }
  styles;
}

handleTimer(delay, styles) {
  let timerID = setTimeout(() => {
    console.log(delay);
    this.element.style = styles
  }, delay);
  return timerID
}

// In the refactored solution, I realized the closure was superflous
// double yay, let = concise code
animate() {
  let delaySoFar = 0;
  let styles = null;
  for (let sequence of this.dataSet) {
    let delay = sequence[0] + delaySoFar;
    let objects = sequence.filter(this.isObject);
    let styles = this.formatStyles(objects);  

    setTimeout(() => {
      this.element.style = styles;
    }, delay);

    delaySoFar = delay;
  }
  styles;
}