JavaScript task queue

gistfile1.js

var queue = function() {
  var tasks;

  return {
    start: function( list ) {
      tasks = list;
      first = tasks.pop();
      first();
    },

    next: function() {
      if ( tasks.length > 0 ) {
        tasks.pop()();
      }
    }
  }
}

// example implementation
task_fn = function(i) {
  return function() {
    console.log( "started " + i );
    window.setTimeout( done_fn(i), 1000 );
  }
}

done_fn = function(i) {
  return function() {
    console.log( "finished " + i );
    q.next();
  }
}

var 
  q = queue(),
  todo = [ task_fn( 'a' ), task_fn( 'b' ), task_fn( 'c' ) ];
q.start( todo );