fix(loki): cloning method for specific classes (#30)

(from techfort/LokiJS#586)

packages/loki/spec/generic/cloning.spec.js

@@ -65,6 +65,29 @@ describe("cloning behavior", () => {
     });
   });
 
+  describe("cloning method \"shallow\" save prototype", function () {
+    it("works", () => {
+      function Item(name, owner, maker) {
+        this.name = name;
+        this.owner = owner;
+        this.maker = maker;
+      }
+
+      const cdb = new loki("clonetest");
+      const citems = cdb.addCollection("items", {clone: true, cloneMethod: "shallow"});
+      const oldObject = new Item("mjolnir", "thor", "dwarves");
+      const insObject = citems.insert(oldObject);
+
+      // cant' have either of these polluting our collection
+      oldObject.name = "mewmew";
+      insObject.name = "mewmew";
+
+      const result = citems.findOne({"owner": "thor"});
+      expect(result instanceof Item).toBe(true);
+      expect(result.name).toBe("mjolnir");
+    });
+  });
+
   describe("collection find() cloning works", () => {
     it("works", () => {
       const cdb = new loki("cloningEnabled");

packages/loki/src/clone.js

@@ -16,14 +16,14 @@ export function clone(data, method) {
       break;
     case "shallow":
       // more compatible method for older browsers
-      cloned = data.prototype ? Object.create(data.prototype) : {};
+      cloned = Object.create(data.constructor.prototype);
       Object.keys(data).map((i) => {
         cloned[i] = data[i];
       });
       break;
     case "shallow-assign":
       // should be supported by newer environments/browsers
-      cloned = data.prototype ? Object.create(data.prototype) : {};
+      cloned = Object.create(data.constructor.prototype);
       Object.assign(cloned, data);
       break;
     default: