title: Promises on non-supported browsers
body: <p>My web page is potentially loaded by some old browsers (specifically, in an Android app with WebView, which may still be used by some pretty old devices)... not that many so I don't want to go to too much trouble to support them fully, but I at least want the page to load.  So, I'd rather not resort to transpilers etc to back everything fully backward compatible.</p>
  
  <p>So how do I make my code "safe" to use on the older browsers?  Those parts of my code that use promises are "optional" in the sense that if they are not accessible then the page will still be of use.  So I'd like some way of including promises in my code without it breaking things for older browsers.</p>
  
  <p>Is it enough to put these parts inside a check for promise support, like <code>if (window.Promise) { myPromise = getMeAPromise(); mPromise.then(...).catch(...); }</code> so that these parts would never be reached by the interpreter?  Or is there a compilation process that would still cause this to fail on a non-supported browser?</p>