Use JavaScript's definition of falsy

Fixes #186

mustache.js

@@ -286,10 +286,9 @@ var Mustache;
   Renderer.prototype._inverted = function (name, context, callback) {
     var value = context.lookup(name);
 
-    // From the spec: inverted sections may render text once based on the
-    // inverse value of the key. That is, they will be rendered if the key
-    // doesn't exist, is false, or is an empty list.
-    if (value == null || value === false || (isArray(value) && value.length === 0)) {
+    // Use JavaScript's definition of falsy. Include empty arrays.
+    // See https://github.com/janl/mustache.js/issues/186
+    if (!value || (isArray(value) && value.length === 0)) {
       return callback(context, this);
     }
 

test/_files/falsy.js

@@ -0,0 +1,8 @@
+({
+  "emptyString": "",
+  "emptyArray": [],
+  "zero": 0,
+  "null": null,
+  "undefined": undefined,
+  "NaN": 0/0
+})

test/_files/falsy.mustache

@@ -0,0 +1,12 @@
+{{#emptyString}}empty string{{/emptyString}}
+{{^emptyString}}inverted empty string{{/emptyString}}
+{{#emptyArray}}empty array{{/emptyArray}}
+{{^emptyArray}}inverted empty array{{/emptyArray}}
+{{#zero}}zero{{/zero}}
+{{^zero}}inverted zero{{/zero}}
+{{#null}}null{{/null}}
+{{^null}}inverted null{{/null}}
+{{#undefined}}undefined{{/undefined}}
+{{^undefined}}inverted undefined{{/undefined}}
+{{#NaN}}NaN{{/NaN}}
+{{^NaN}}inverted NaN{{/NaN}}

test/_files/falsy.txt

@@ -0,0 +1,12 @@
+
+inverted empty string
+
+inverted empty array
+
+inverted zero
+
+inverted null
+
+inverted undefined
+
+inverted NaN