duffs-device-improved.js

var iterations = Math.floor(values.length / 8);
var leftover = values.length % 8; 
var i = 0;
if ( leftover > 0 )
{
  do {
    process( values[i++] );
  } while ( --leftover > 0 );
} 
do {                   
  process(values[i++]);
  process(values[i++]);
  process(values[i++]);
  process(values[i++]);
  process(values[i++]);
  process(values[i++]);
  process(values[i++]);
  process(values[i++]);
} while ( --iterations > 0 );

duffs-device.js

var iterations = Math.ceil( values.length / 8 ); 
var startAt = values.length % 8; 
var i = 0;
do {
  switch(startAt)
  {
    case 0: process(values[i++]);
    case 7: process(values[i++]);
    case 6: process(values[i++]);
    case 5: process(values[i++]);
    case 4: process(values[i++]);
    case 3: process(values[i++]);
    case 2: process(values[i++]);
    case 1: process(values[i++]);
  }
  startAt = 0;
} while (--iterations > 0);