working example

example/copy.js

@@ -0,0 +1,8 @@
+var copy = require('../');
+
+var obj = { a: 3, b: 4, c: 5 };
+var dup = copy(obj);
+dup.b *= 111;
+
+console.log('original: ', obj);
+console.log('copy: ', dup);

index.js

@@ -0,0 +1,35 @@
+module.exports = function (obj) {
+    if (!obj || typeof obj !== 'object') return obj;
+
+    var copy;
+
+    if (isArray(obj)) {
+        var len = obj.length;
+        copy = Array(len);
+        for (var i = 0; i < len; i++) {
+            copy[i] = obj[i];
+        }
+    }
+    else {
+        var keys = objectKeys(obj);
+        copy = {};
+
+        for (var i = 0, l = keys.length; i < l; i++) {
+            var key = keys[i];
+            copy[key] = obj[key];
+        }
+    }
+    return copy;
+};
+
+var objectKeys = Object.keys || function (obj) {
+    var keys = [];
+    for (var key in keys) {
+        if ({}.hasOwnProperty.call(obj, key)) keys.push(key);
+    }
+    return keys;
+};
+
+var isArray = Array.isArray || function (xs) {
+    return {}.toString.call(xs) === '[object Array]';
+};