title: How to remove TypeScript warning: property 'length' does not exist on type '{}'
body: <p>In a TypeScript file, I have defined a 3D array:</p>
  
  <pre><code>var myArr = ['one', [[19, 1], [13, 1], [86, 1], [12, 2]],
               'two',    [[83, 1], [72, 1], [16, 2]],
               'three',  [[4, 1]]];
  
  function testArray(){
      console.log(myArr[1].length);
  }
  </code></pre>
  
  <p>I get a warning under the length property: </p>
  
  <blockquote>
    <p>Property 'length' does not exist on type '{}'</p>
  </blockquote>
  
  <p>Is there something I can do to remove this warning?</p>