From 221161ceccd224f9b0f871426ddd656f358a2f5b Mon Sep 17 00:00:00 2001
From: Michael Ficarra <git@michael.ficarra.me>
Date: Tue, 4 Oct 2011 22:24:36 -0400
Subject: [PATCH] better isXXX checks; the current tests have too many false
 positives

---
 test/objects.js |  5 +++--
 underscore.js   | 17 +++++++++--------
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/test/objects.js b/test/objects.js
index e05c0ddc5..0e1f3e4f3 100644
--- a/test/objects.js
+++ b/test/objects.js
@@ -383,14 +383,15 @@ $(document).ready(function() {
     ok(!_.isNumber(arguments), 'the arguments object is not a number');
     ok(!_.isNumber(undefined), 'undefined is not a number');
     ok(_.isNumber(3 * 4 - 7 / 10), 'but numbers are');
-    ok(!_.isNumber(NaN), 'NaN is not a number');
+    ok(_.isNumber(NaN), 'NaN *is* a number');
     ok(_.isNumber(Infinity), 'Infinity is a number');
     ok(_.isNumber(iNumber), 'even from another frame');
+    ok(!_.isNumber('1'), 'numeric strings are not numbers');
   });
 
   test("objects: isBoolean", function() {
     ok(!_.isBoolean(2), 'a number is not a boolean');
-   	ok(!_.isBoolean("string"), 'a string is not a boolean');
+    ok(!_.isBoolean("string"), 'a string is not a boolean');
     ok(!_.isBoolean("false"), 'the string "false" is not a boolean');
     ok(!_.isBoolean("true"), 'the string "true" is not a boolean');
     ok(!_.isBoolean(arguments), 'the arguments object is not a boolean');
diff --git a/underscore.js b/underscore.js
index 0db66d0b6..182070eb3 100644
--- a/underscore.js
+++ b/underscore.js
@@ -714,7 +714,8 @@
     return eq(a, b, []);
   };
 
-  // Is a given array or object empty?
+  // Is a given array, string, or object empty?
+  // An "empty" object has no enumerable own-properties.
   _.isEmpty = function(obj) {
     if (_.isArray(obj) || _.isString(obj)) return obj.length === 0;
     for (var key in obj) if (hasOwnProperty.call(obj, key)) return false;
@@ -729,7 +730,7 @@
   // Is a given value an array?
   // Delegates to ECMA5's native Array.isArray
   _.isArray = nativeIsArray || function(obj) {
-    return toString.call(obj) === '[object Array]';
+    return toString.call(obj) == '[object Array]';
   };
 
   // Is a given variable an object?
@@ -739,22 +740,22 @@
 
   // Is a given variable an arguments object?
   _.isArguments = function(obj) {
-    return !!(obj && hasOwnProperty.call(obj, 'callee'));
+    return toString.call(obj) == '[object Arguments]' || !!(obj && hasOwnProperty.call(obj, 'callee'));
   };
 
   // Is a given value a function?
   _.isFunction = function(obj) {
-    return !!(obj && obj.constructor && obj.call && obj.apply);
+    return toString.call(obj) == '[object Function]';
   };
 
   // Is a given value a string?
   _.isString = function(obj) {
-    return !!(obj === '' || (obj && obj.charCodeAt && obj.substr));
+    return toString.call(obj) == '[object String]';
   };
 
   // Is a given value a number?
   _.isNumber = function(obj) {
-    return !!(obj === 0 || (obj && obj.toExponential && obj.toFixed));
+    return toString.call(obj) == '[object Number]';
   };
 
   // Is the given value `NaN`? `NaN` happens to be the only value in JavaScript
@@ -770,12 +771,12 @@
 
   // Is a given value a date?
   _.isDate = function(obj) {
-    return !!(obj && obj.getTimezoneOffset && obj.setUTCFullYear);
+    return toString.call(obj) == '[object Date]';
   };
 
   // Is the given value a regular expression?
   _.isRegExp = function(obj) {
-    return !!(obj && obj.test && obj.exec && (obj.ignoreCase || obj.ignoreCase === false));
+    return toString.call(obj) == '[object RegExp]';
   };
 
   // Is a given value equal to null?