title: jQuery, 'undefined' length of array of arrays?
body: <p>I have this array structure:</p>
  
  <pre><code>mdarray = {
    '0001':{address:'add1',title:'title1'},
    '0002':{address:'add2',title:'title2'},
    '0003':{address:'add3',title:'title3'}
  };
  </code></pre>
  
  <p>I wish to only work with the array if it has one or more items in it. Usually with an array I would use <code>if (mdarray.length &gt; 0) {}</code> but when I do this with the array above, <code>mdarray.length</code> returns 'undefined'.</p>
  
  <p>Is this is because it is an array of arrays? Is there another way to very simply pull back the number if items in the root of the array?</p>
  
  <p>Or it is because the keys are strings and not integers?</p>
  
  <p>I've played about with different array structures and read about multidimensional arrays but I've not yet found an answer.</p>