ESNext compatibility (dexie#812)

* Check tests pass forcing Promise

Also removed template literal to plain string, as not templating needed

* Tests passed - check _global.Promise

all 239 tests passed on my machine with the prior commit (which would have been bypassed with the current if clause when running on a browser)

src/functions/utils.ts

@@ -1,10 +1,14 @@
 declare var global;
 export const keys = Object.keys;
 export const isArray = Array.isArray;
-export const _global =
+const _global =
     typeof self !== 'undefined' ? self :
     typeof window !== 'undefined' ? window :
     global;
+if (!_global.Promise){
+    _global.Promise = Promise;
+}
+export { _global }
 
 export function extend(obj, extension) {
     if (typeof extension !== 'object') return obj;

src/helpers/promise.js

@@ -44,7 +44,7 @@ const
     nativePromiseInstanceAndProto = (()=>{
         try {
             // Be able to patch native async functions
-            return new Function(`let F=async ()=>{},p=F();return [p,Object.getPrototypeOf(p),Promise.resolve(),F.constructor];`)();
+            return new Function('let F=async ()=>{},p=F();return [p,Object.getPrototypeOf(p),Promise.resolve(),F.constructor];')();
         } catch(e) {
             var P = _global.Promise;
             return P ?