Test if can function as a promise. Copied from paypal sdk/js for subscriptions

is_promise_like.js

function is_promise_like(n) {
  try {
      if (!n)
          {cl('falsy'); return !1; } 
      if ("undefined" != typeof Promise && n instanceof Promise)
          {cl('is Promise (ok)'); return !0; } 
      if ("undefined" != typeof window && "function" == typeof window.Window && n instanceof window.Window)
          {cl('is Window'); return !1; } 
      if ("undefined" != typeof window && "function" == typeof window.constructor && n instanceof window.constructor)
          {cl('is constructor'); return !1; } 
      var e = {}.toString;
      if (e) { 
          var t = e.call(n);
          if ("[object Window]" === t || "[object global]" === t || "[object DOMWindow]" === t)
              {cl('obj type'); return !1 }
      }     
      if ("function" == typeof n.then)
          {cl('has then (ok)'); return !0 }
  } catch (n) { 
      cl('exception');
      return !1
  }     
  cl('other');
  return !1
}