Optimising JavaScript performances with asynchronous loops

specificTimeCheck.js

function splitLoop(items, process, context, callback) {
  var todo = items.concat();
  
  setTimeout(function () {
    var start = +new Date();
    
    do { 
      process.call(context, todo.shift());
    } while (todo.length > 0 && (+new Date() - start < 50));
    
    if (todo.length > 0) { 
      setTimeout(arguments.callee, 25);
    } else { 
      callback(items);
    }
  }, 25);
}