added unit testing, and started implementing unit tests...phew

node_modules/just-extend/index.js

@@ -0,0 +1,62 @@
+module.exports = extend;
+
+/*
+  var obj = {a: 3, b: 5};
+  extend(obj, {a: 4, c: 8}); // {a: 4, b: 5, c: 8}
+  obj; // {a: 4, b: 5, c: 8}
+
+  var obj = {a: 3, b: 5};
+  extend({}, obj, {a: 4, c: 8}); // {a: 4, b: 5, c: 8}
+  obj; // {a: 3, b: 5}
+
+  var arr = [1, 2, 3];
+  var obj = {a: 3, b: 5};
+  extend(obj, {c: arr}); // {a: 3, b: 5, c: [1, 2, 3]}
+  arr.push(4);
+  obj; // {a: 3, b: 5, c: [1, 2, 3, 4]}
+
+  var arr = [1, 2, 3];
+  var obj = {a: 3, b: 5};
+  extend(true, obj, {c: arr}); // {a: 3, b: 5, c: [1, 2, 3]}
+  arr.push(4);
+  obj; // {a: 3, b: 5, c: [1, 2, 3]}
+
+  extend({a: 4, b: 5}); // {a: 4, b: 5}
+  extend({a: 4, b: 5}, 3); {a: 4, b: 5}
+  extend({a: 4, b: 5}, true); {a: 4, b: 5}
+  extend('hello', {a: 4, b: 5}); // throws
+  extend(3, {a: 4, b: 5}); // throws
+*/
+
+function extend(/* [deep], obj1, obj2, [objn] */) {
+  var args = [].slice.call(arguments);
+  var deep = false;
+  if (typeof args[0] == 'boolean') {
+    deep = args.shift();
+  }
+  var result = args[0];
+  if (!result || (typeof result != 'object' && typeof result != 'function')) {
+    throw new Error('extendee must be an object');
+  }
+  var extenders = args.slice(1);
+  var len = extenders.length;
+  for (var i = 0; i < len; i++) {
+    var extender = extenders[i];
+    for (var key in extender) {
+      if (extender.hasOwnProperty(key)) {
+        var value = extender[key];
+        if (deep && isCloneable(value)) {
+          var base = Array.isArray(value) ? [] : {};
+          result[key] = extend(true, result.hasOwnProperty(key) ? result[key] : base, value);
+        } else {
+          result[key] = value;
+        }
+      }
+    }
+  }
+  return result;
+}
+
+function isCloneable(obj) {
+  return Array.isArray(obj) || {}.toString.call(obj) == '[object Object]';
+}