deepAssign keeps prototypal chain of copied properties now (closes #110)

Author: RobinBuschmann

lib/utils/object.ts

@@ -20,43 +20,38 @@ export function deepAssign(target: any, ...sources: any[]): any {
   return target;
 
   function assign(key: string | number, _target: any, _source: any): void {
-
     const sourceValue = _source[key];
-    if (sourceValue !== void 0) {
 
+    if (sourceValue !== void 0) {
       let targetValue = _target[key];
 
       if (Array.isArray(sourceValue)) {
-
         if (!Array.isArray(targetValue)) {
           targetValue = [];
         }
-
         const length = targetValue.length;
 
         sourceValue.forEach((_, index) => assign(length + index, targetValue, sourceValue));
-
       } else if (typeof sourceValue === 'object') {
-
-        targetValue = targetValue || {};
-
         if (sourceValue instanceof RegExp) {
-
           targetValue = cloneRegExp(sourceValue);
         } else if (sourceValue instanceof Date) {
-
           targetValue = new Date(sourceValue);
         } else if (sourceValue === null) {
-
           targetValue = null;
         } else {
+          if (!targetValue) {
+            if (sourceValue.constructor && sourceValue.constructor.prototype) {
+              targetValue = Object.create(sourceValue.constructor.prototype);
+            } else {
+              targetValue = {};
+            }
+          }
           deepAssign(targetValue, sourceValue);
         }
       } else {
-
         targetValue = sourceValue;
       }
-
       _target[key] = targetValue;
     }
   }
@@ -100,7 +95,7 @@ export function getAllPropertyNames(obj: any): string[] {
     obj = Object.getPrototypeOf(obj);
   } while (obj !== Object.prototype);
 
-  const exists: {[name: string]: boolean|undefined} = {};
+  const exists: { [name: string]: boolean | undefined } = {};
 
   return names.filter(name => {
 

test/specs/utils/object.spec.ts

@@ -108,6 +108,16 @@ describe('utils', () => {
 
       });
 
+      it('should keep prototype chain', () => {
+        class Test {
+          protoFn(): any {}
+        }
+        const copy = deepAssign({}, {test: new Test()});
+
+        expect(copy.test)
+          .to.have.property('protoFn')
+          .that.is.a('function');
+      });
 
     });