Format milliseconds to human time

index.js

const format = time => [ time, 3600000, 60000, 1000, 1 ]
  .reduce( ( parts, d, i, arr ) => {
    if ( i === 0 ) { return parts; }
    const p = Math.floor( arr[0] / d ); 
    arr[0] = arr[0] - (p * d);
    return parts.concat( p ); 
  }, [] ).map( t => String( t ).padStart( 2, '0' ) ).join(':');