title: JavaScript6: adding element (key, value) to a ES6 map
body: <p>In jsx I have a map like:  </p>
  
  <pre><code>var myMap=Map([['rowNumber', '30'], ['id', '80'], ['firstName', '180'], ['lastName', '180'], ['mobile', '180'], ['username', '180'], ['password', '180']])
  </code></pre>
  
  <p>how can I do programatically add new element like: ['ssn', '12']
  to this map?</p>