fix: clone custom class instances;

- Closes #14
- Removes invalid test case

src/index.js

@@ -4,17 +4,26 @@ export default function klona(x) {
 	var k, tmp, str=Object.prototype.toString.call(x);
 
 	if (str === '[object Object]') {
-		tmp = {};
-		for (k in x) {
-			if (k === '__proto__') {
-				Object.defineProperty(tmp, k, {
-					value: klona(x[k]),
-					configurable: 1,
-					enumerable: 1,
-					writable: 1,
-				});
-			} else {
-				tmp[k] = klona(x[k]);
+		if (x.constructor !== Object && typeof x.constructor === 'function') {
+			tmp = new x.constructor();
+			for (k in x) {
+				if (tmp[k] === void 0) {
+					tmp[k] = klona(x[k]);
+				}
+			}
+		} else {
+			tmp = {}; // null
+			for (k in x) {
+				if (k === '__proto__') {
+					Object.defineProperty(tmp, k, {
+						value: klona(x[k]),
+						configurable: true,
+						enumerable: true,
+						writable: true,
+					});
+				} else {
+					tmp[k] = klona(x[k]);
+				}
 			}
 		}
 		return tmp;

test/index.js

@@ -65,39 +65,30 @@ Classes('class', () => {
 	const output = klona(input);
 
 	assert.deepEqual(input, output);
+	assert.equal(input.constructor, output.constructor);
+	assert.equal(output.constructor.name, 'Foobar');
 
 	output.foobar = 123;
 	// @ts-ignore
 	assert.notEqual(input.foobar, 123);
 });
 
-Classes.run();
-
-// ---
-
-const Constructor = suite('constructor');
-
-Constructor('hijack', () => {
-	let count = 0;
-
-	class Foo {}
-	function CustomArray() {
-		count++;
-	}
-
-	const input = new Foo();
-	assert.equal(input.constructor.name, 'Foo');
-
-	input.constructor = CustomArray;
-	assert.equal(input.constructor.name, 'CustomArray');
+// @see https://github.com/lukeed/klona/issues/14
+Classes('prototype', () => {
+	function Test () {}
+	Test.prototype.val = 42;
 
+	const input = new Test();
 	const output = klona(input);
+
 	assert.deepEqual(input, output);
 
-	assert.equal(count, 0, '~> did not call constructor');
+	assert.deepEqual(output.constructor, Test);
+	assert.deepEqual(output.__proto__, { val: 42 });
+	assert.deepEqual(output, {});
 });
 
-Constructor.run();
+Classes.run();
 
 // ---