index.html

<div class="root">
  <div class="outer">
    <div class="box1 box"></div>
    <div class="box2 box"></div>
    <div class="box3 box"></div>
    <div class="box4 box"></div>
  </div>
</div>

Gozala

// Utility function for detecting generators.
let isGenerator = x => {
  return Function.isGenerator &&
         Function.isGenerator.call(x)
}

// Data type represents channel into which values
// can be `put`, or `received` from. Channel is
// very much like queue where reads and writes are
// synchronized via continuation passing.