title: ES5 this.method is not a function
body: <p>I have a typescript 2 class that targets ES5.  I'm getting the err in the subject line in the console when I run it.  The switch statement works fine, but increment() and decrement() methods don't execute.</p>
  
  <pre><code>class MyClass extends React.Component{
    ...
    increment() {
      console.log('increment()')
      ...
    }
    decrement() {
      console.log('decrement()')
      ...
    }
  
    buttonClick(btn) {
      console.log(btn)
      switch (btn) {
          case "prev":
              console.log('switch prev')
              this.decrement();
              //this.decrement;
              break;
          default:
              console.log('switch next')
              this.increment();
              //this.increment; eliminates err but method still doesnt execute
              break;
      }
    }
  }
  </code></pre>