relax()

gistfile1.txt

function relax(callback, startIndex, dataLength, chunkSize, delay) {
  chunkSize = chunkSize || 1000;
  delay = delay || 1;

  var endIndex = startIndex + Math.min((dataLength-startIndex), chunkSize);

  if (startIndex === endIndex) {
    return;
  }

  callback(startIndex, endIndex);

  if (startIndex < dataLength) {
    setTimeout(function() {
      relax(callback, endIndex, dataLength, chunkSize, delay);
    }, delay);
  }
}