fix(web): Gracefully degrade Proxy usage to fix IE11 (#2759)

core/src/web-runtime.ts

@@ -10,26 +10,31 @@ export class CapacitorWeb {
     // get the typed benefits of the provided plugins in PluginRegistry
     this.Plugins = {} as any;
 
-    // Build a proxy for the Plugins object that returns the "Noop Plugin"
-    // if a plugin isn't available
-    this.Plugins = new Proxy<any>(this.Plugins, {
-      get: (target, prop) => {
-        if (typeof target[prop] === 'undefined') {
-          let thisRef = this;
-          return new Proxy<any>({}, {
-            get: (_target, _prop) => {
-              if (typeof _target[_prop] === 'undefined') {
-                return thisRef.pluginMethodNoop.bind(thisRef, _target, _prop,  prop);
-              } else {
-                return _target[_prop];
+    // Gracefully degrade in non-Proxy supporting engines, e.g. IE11. This
+    // effectively means that trying to access an unavailable plugin will
+    // locally throw, but this is still better than throwing a syntax error.
+    if ('Proxy' in window) {
+      // Build a proxy for the Plugins object that returns the "Noop Plugin"
+      // if a plugin isn't available
+      this.Plugins = new Proxy<any>(this.Plugins, {
+        get: (target, prop) => {
+          if (typeof target[prop] === 'undefined') {
+            let thisRef = this;
+            return new Proxy<any>({}, {
+              get: (_target, _prop) => {
+                if (typeof _target[_prop] === 'undefined') {
+                  return thisRef.pluginMethodNoop.bind(thisRef, _target, _prop,  prop);
+                } else {
+                  return _target[_prop];
+                }
               }
-            }
-          });
-        } else {
-          return target[prop];
+            });
+          } else {
+            return target[prop];
+          }
         }
-      }
-    });
+      });
+    }
   }
 
   pluginMethodNoop(_target: any, _prop: PropertyKey, pluginName: string) {