title: How to get the size of keys in map?
body: <p>Lets say I have this map:</p>
  
  <pre><code>var myMap = new Map();
  myMap.set('0', 'foo');
  myMap.set(1, 'bar');
  myMap.set({}, 'baz');
  
  var size= myMap.keys().size(); // wrong. 
  
  console.log(size); //Looking for 3 because there are 3 keys
  </code></pre>
  
  <p>Is there a way? Or any alternative? Much appreciated. </p>