diff --git a/source/Ox/js/Type.js b/source/Ox/js/Type.js
index fb710a71..2bec9120 100644
--- a/source/Ox/js/Type.js
+++ b/source/Ox/js/Type.js
@@ -1,5 +1,17 @@
 'use strict';
 
+/*@
+Ox.checkType <f> Throws a TypeError if a value is not of a given type
+    (val, type) -> <u> undefined
+    val <*> Any value
+    type <s> Type
+@*/
+Ox.checkType = function(val, type) {
+    if (!Ox.in(Ox.makeArray(type), Ox.typeOf(val))) {
+        throw new TypeError();
+    }
+};
+
 /*@
 Ox.isArguments <f> Tests if a value is an arguments "array"
     (value) -> <b> True if the value is an arguments "array"
@@ -8,15 +20,8 @@ Ox.isArguments <f> Tests if a value is an arguments "array"
     true
 @*/
 Ox.isArguments = function(val) {
-    return !!(val && val.toString() == '[object Arguments]');
-}
-if (!(function() {
-    return Ox.isArguments(arguments);
-}())) {
-    Ox.isArguments = function(val) {
-        return !!(val && Object.hasOwnProperty.call(val, 'callee'));
-    };
-}
+    return Ox.typeOf(val) == 'arguments';
+};
 
 /*@
 Ox.isArray <f> Tests if a value is an array
@@ -30,8 +35,8 @@ Ox.isArray <f> Tests if a value is an array
     false
 @*/
 Ox.isArray = function(val) {
-    return val instanceof Array;
-}
+    return Ox.typeOf(val) == 'array';
+};
 
 /*@
 Ox.isBoolean <f> Tests if a value is boolean
@@ -41,7 +46,7 @@ Ox.isBoolean <f> Tests if a value is boolean
     true
 @*/
 Ox.isBoolean = function(val) {
-    return typeof val == 'boolean';
+    return Ox.typeOf(val) == 'boolean';
 };
 
 /*@
@@ -52,18 +57,18 @@ Ox.isDate <f> Tests if a value is a date
     true
 @*/
 Ox.isDate = function(val) {
-    return val instanceof Date;
+    return Ox.typeOf(val) == 'date';
 };
 
 /*@
 Ox.isElement <f> Tests if a value is a DOM element
     (value) -> <b> True if the value is a DOM element
     value <*> Any value
-    > Ox.isElement(document.createElement())
+    > Ox.isElement(document.createElement('a'))
     true
 @*/
 Ox.isElement = function(val) {
-    return !!(val && val.nodeType == 1);
+    return Ox.endsWith(Ox.typeOf(val), 'element');
 };
 
 /*@
@@ -152,12 +157,12 @@ Ox.isFunction <f> Tests if a value is a function
     false
 @*/
 Ox.isFunction = function(val) {
-    return typeof val == 'function' && !Ox.isRegExp(val);
+    return Ox.typeOf(val) == 'function';
 };
 
 /*@
-Ox.isInfinity <f> Tests if a value is infinite
-    (value) -> <b> True if the value is infinite
+Ox.isInfinity <f> Tests if a value is positive or negative Infinity
+    (value) -> <b> True if the value is positive or negative Infinity
     value <*> Any value
     > Ox.isInfinity(Infinity)
     true
@@ -167,17 +172,29 @@ Ox.isInfinity <f> Tests if a value is infinite
     false
 @*/
 Ox.isInfinity = function(val) {
-    return typeof val == 'number' && !isFinite(val) && !Ox.isNaN(val);
+    return Ox.typeOf(val) == 'number' && !isFinite(val) && !Ox.isNaN(val);
 };
 
 /*@
-Ox.isNaN <f> Tests if a value is "Not a Number"
-    (value) -> <b> True if the value is "Not a Number"
+Ox.isInt <f> Tests if a value is an integer
+    (value) -> <b> True if the value is an integer
+    value <*> Any value
+    > Ox.isInt(0)
+    true
+    > Ox.isInt(0.5)
+    false
+@*/
+Ox.isInt = function(val) {
+    return val === Math.floor(val);
+};
+
+/*@
+Ox.isNaN <f> Tests if a value is NaN
+    (value) -> <b> True if the value is NaN
     value <*> Any value
     > Ox.isNaN(NaN)
     true
 @*/
-
 Ox.isNaN = function(val) {
     return val !== val;
 }
@@ -190,7 +207,7 @@ Ox.isNull <f> Tests if a value is <code>null</code>
     true
 @*/
 Ox.isNull = function(val) {
-    return val === null;
+    return Ox.typeOf(val) == 'null';
 };
 
 /*@
@@ -206,9 +223,8 @@ Ox.isNumber <f> Tests if a value is a number
     > Ox.isNumber(NaN)
     false
 @*/
-
 Ox.isNumber = function(val) {
-    return typeof val == 'number' && isFinite(val);
+    return Ox.typeOf(val) == 'number';
 };
 
 /*@
@@ -226,11 +242,28 @@ Ox.isObject <f> Tests if a value is a an object
     > Ox.isObject(/ /)
     false
 @*/
-
 Ox.isObject = function(val) {
-    return typeof val == 'object' && !Ox.isArguments(val)
-        && !Ox.isArray(val) && !Ox.isDate(val)
-        && !Ox.isNull(val) && !Ox.isRegExp(val);
+    return Ox.typeOf(val) == 'object';
+};
+
+/*@
+Ox.isPrimitive <f> Tests if a value is a primitive (boolean, number or string)
+    (value) -> <b> True if the value is a primitive
+    value <*> Any value
+    > Ox.isPrimitive(false)
+    true
+    > Ox.isPrimitive(0)
+    true
+    > Ox.isPrimitive('')
+    true
+    > Ox.isPrimitive([])
+    false
+    > Ox.isPrimitive({})
+    false
+@*/
+Ox.isPrimitive = function(val) {
+    var type = Ox.typeOf(val);
+    return type == 'boolean' || type == 'number' || type == 'string';
 };
 
 /*@
@@ -240,9 +273,8 @@ Ox.isRegExp <f> Tests if a value is a regular expression
     > Ox.isRegExp(/ /)
     true
 @*/
-
 Ox.isRegExp = function(val) {
-    return val instanceof RegExp;
+    return Ox.typeOf(val) == 'regexp';
 };
 
 /*@
@@ -252,9 +284,8 @@ Ox.isString <f> Tests if a value is a string
     > Ox.isString('')
     true
 @*/
-
 Ox.isString = function(val) {
-    return typeof val == 'string';
+    return Ox.typeOf(val) == 'string';
 };
 
 /*@
@@ -264,53 +295,45 @@ Ox.isUndefined <f> Tests if a value is undefined
     > Ox.isUndefined()
     true
 @*/
-
 Ox.isUndefined = function(val) {
-    return val === void 0;
+    return Ox.typeOf(val) == 'undefined';
 };
 
 /*@
 Ox.typeOf <f> Returns the type of a value
-    (value) -> <s> type
+    (value) -> <s> Type
     value <*> Any value
-    # Examples
     > (function() { return Ox.typeOf(arguments); }())
-    "arguments"
+    'arguments'
     > Ox.typeOf([])
-    "array"
+    'array'
     > Ox.typeOf(false)
-    "boolean"
+    'boolean'
     > Ox.typeOf(new Date())
-    "date"
-    > Ox.typeOf(document.createElement())
-    "element"
+    'date'
     > Ox.typeOf(function() {})
-    "function"
-    > Ox.typeOf(Infinity)
-    "infinity"
-    > Ox.typeOf(NaN)
-    "nan"
+    'function'
+    > Ox.typeOf(document.createElement('a'))
+    "htmlanchorelement"
+    > Ox.typeOf(document.getElementsByTagName('a'))
+    'nodelist'
     > Ox.typeOf(null)
-    "null"
+    'null'
     > Ox.typeOf(0)
-    "number"
+    'number'
+    > Ox.typeOf(Infinity)
+    'number'
+    > Ox.typeOf(NaN)
+    'number'
     > Ox.typeOf({})
-    "object"
+    'object'
     > Ox.typeOf(/ /)
-    "regexp"
+    'regexp'
     > Ox.typeOf('')
-    "string"
+    'string'
     > Ox.typeOf()
-    "undefined"
+    'undefined'
 @*/
-
 Ox.typeOf = function(val) {
-    var ret;
-    Ox.forEach(Ox.TYPES, function(type) {
-        if (Ox['is' + type](val)) {
-            ret = type.toLowerCase();
-            return false;
-        }
-    });
-    return ret;
-};
\ No newline at end of file
+    return Object.prototype.toString.call(val).slice(8, -1).toLowerCase();
+};