3 files changed, 53 insertions, 0 deletions
diff --git a/util/deep_assign.ts b/util/deep_assign.ts
new file mode 100644
index 000000000..4857e18b5
--- /dev/null
+++ b/util/deep_assign.ts
@@ -0,0 +1,28 @@
+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+export function deepAssign(target: object, ...sources: object[]): object {
+  for (let i = 0; i < sources.length; i++) {
+    const source = sources[i];
+    if (!source || typeof source !== `object`) {
+      return;
+    }
+    Object.entries(source).forEach(([key, value]) => {
+      if (value instanceof Date) {
+        target[key] = new Date(value);
+        return;
+      }
+      if (!value || typeof value !== `object`) {
+        target[key] = value;
+        return;
+      }
+      if (Array.isArray(value)) {
+        target[key] = [];
+      }
+      // value is an Object
+      if (typeof target[key] !== `object` || !target[key]) {
+        target[key] = {};
+      }
+      deepAssign(target[key], value);
+    });
+  }
+  return target;
+}
diff --git a/util/deep_assign_test.ts b/util/deep_assign_test.ts
new file mode 100644
index 000000000..36be979d8
--- /dev/null
+++ b/util/deep_assign_test.ts
@@ -0,0 +1,24 @@
+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+import { test } from "../testing/mod.ts";
+import { assertEquals, assert } from "../testing/asserts.ts";
+import { deepAssign } from "./deep_assign.ts";
+
+test(function deepAssignTest() {
+  const date = new Date("1979-05-27T07:32:00Z");
+  const reg = RegExp(/DENOWOWO/);
+  const obj1 = { deno: { bar: { deno: ["is", "not", "node"] } } };
+  const obj2 = { foo: { deno: date } };
+  const obj3 = { foo: { bar: "deno" }, reg: reg };
+  const actual = deepAssign(obj1, obj2, obj3);
+  const expected = {
+    foo: {
+      deno: new Date("1979-05-27T07:32:00Z"),
+      bar: "deno"
+    },
+    deno: { bar: { deno: ["is", "not", "node"] } },
+    reg: RegExp(/DENOWOWO/)
+  };
+  assert(date !== expected.foo.deno);
+  assert(reg !== expected.reg);
+  assertEquals(actual, expected);
+});
diff --git a/util/test.ts b/util/test.ts
new file mode 100644
index 000000000..a617c10ab
--- /dev/null
+++ b/util/test.ts
@@ -0,0 +1 @@
+import "./deep_assign_test.ts";