title: JavaScript array values turned to undefined when not debugging in IE11
body: <p>I have written a very simple partition function in JavaScript:</p>
  
  <pre><code>Array.prototype.partition = function (size, step) {
      var out = [];
  
      for (var i = 0; i &lt; this.length - size; i += step) {
          var tmp = this.slice(i, i + size);
          //two lines below were for quick debug
          //console.log(tmp);
          //console.log(out);
          out.push(tmp);
      }
  
      return out;
  };
  </code></pre>
  
  <p>Example usage:</p>
  
  <pre><code>var arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
  console.log(arr);
  console.log(arr.partition(2, 1));
  </code></pre>
  
  <p>When running in latest Firefox it works like expected:</p>
  
  <pre><code>[[1,2],[2,3],[3,4],[4,5],[5,6],[6,7],[7,8],[8,9],[9,10]]
  </code></pre>
  
  <p>I have big issues with it in IE11 though.
  If I run that script without any breakpoints in the mentioned function, it seems like all values in the returned array are 'undefined':
  <img src="https://i.stack.imgur.com/Bc5h5.png" alt="No-breakpoints"></p>
  
  <p>If, however I set at least one breakpoint within the function (in IE debugger), and it pauses within the function on that point, everything seems fine:
  <img src="https://i.stack.imgur.com/OrNO3.png" alt="Breakpoints"></p>
  
  <p>Very strange though that the outputs are at different stages. As you can see without breakpoints both logs are within the same "Navigation occurred" section (whatever that is). While when using breakpoints and debugging, they are in two separate ones.<br>
  Any idea what is going on here? Is it some IE bug? Thanks for your help.  </p>
  
  <p>---EDIT---<br>
  Just realized that despite the fact that these values are being logged in the console as undefined, they in fact are not, and still can be used elsewhere. Seems to me like a logging issue...</p>