代码优化，code review by LZF

@@ -92,9 +92,7 @@ function callpay(orderCode) {
 function isWXOpen() {
     var ua = window.navigator.userAgent.toLowerCase();
 
-    if (ua.indexOf('micromessenger') > 0) {
-        return true;
-    }
+    return ua.indexOf('micromessenger') > 0;
 }
 
 function hideWeChatPay() {