Implementation.

index.js

@@ -0,0 +1,56 @@
+"use strict";
+
+var toString = Object.prototype.toString;
+var has = Object.prototype.hasOwnProperty;
+
+var dateType = '[object Date]';
+var regexType = '[object RegExp]';
+var arrayType = '[object Array]';
+var funcType = '[object Function]';
+var objType = '[object Object]';
+
+module.exports = function isEqual(value, other) {
+	if (value === other) { return true; }
+
+	var type = toString.call(value);
+	if (type !== toString.call(other)) { return false; }
+
+	if (type === dateType) { return value.getTime() === other.getTime(); }
+
+	if (type === regexType) { return String(value) === String(other); }
+
+	if (type === arrayType) {
+		if (value.length !== other.length) { return false; }
+
+		var index = value.length;
+		do {
+			--index;
+		} while (index > 0 && index in value && index in other && isEqual(value[index], other[index]));
+		return index <= 0;
+	}
+
+	if (type === funcType) {
+		return isEqual(value.name, other.name) && isEqual(String(value), String(other));
+	}
+
+	if (type === objType) {
+		if (Object.getPrototypeOf(value) !== Object.getPrototypeOf(other)) { return false; }
+		var key;
+		for (key in value) {
+			if (has.call(value, key)) {
+				if (!(key in other)) { return false; }
+				if (!isEqual(value[key], other[key])) { return false; }
+			}
+		}
+		for (key in other) {
+			if (has.call(other, key)) {
+				if (!(key in value)) { return false; }
+				if (!isEqual(other[key], value[key])) { return false; }
+			}
+		}
+		return true;
+	}
+
+	return false;
+};
+