JavaScript Teaser: Fabulous Fibonacci

Written by Yuri Takhteyev

Fill in the missing line of the following code that implements a function returning the next Fibonacci number every time it's called.

  var nextFibonacciNumber = (function() {
    var s = [0, 1];
    return function () {
      // Fill in the missing line here.
      return s.shift();
    };
  })();

You should only need to add a single statement, consisting of less than 25 characters.

Please post the answer on JSFiddle or similar service, and then post a link to your answer below (so that other people still have a chance to solve it). You can also post other thoughts or email Rangle.io's CTO, Yuri@rangle.io, if you wish to share further ideas.