Check if valueOf is defined. Fixes #176

src/Utility.coffee

@@ -41,11 +41,18 @@ isPlainObject = (val) ->
     (ctor instanceof ctor) and
     (Function.prototype.toString.call(ctor) is Function.prototype.toString.call(Object))
 
+# Gets the primitive value of an object
+getValue = (obj) ->
+  if isFunction obj.valueOf
+    obj.valueOf()
+  else
+    obj
 
 module.exports.assign = assign
 module.exports.isFunction = isFunction
 module.exports.isObject = isObject
 module.exports.isArray = isArray
 module.exports.isEmpty = isEmpty
 module.exports.isPlainObject = isPlainObject
+module.exports.getValue = getValue
 

src/XMLDocumentCB.coffee

@@ -1,4 +1,4 @@
-{ isObject, isFunction, isPlainObject } = require './Utility'
+{ isObject, isFunction, isPlainObject, getValue } = require './Utility'
 
 XMLElement = require './XMLElement'
 XMLCData = require './XMLCData'
@@ -82,10 +82,10 @@ module.exports = class XMLDocumentCB
 
     @openCurrent()
 
-    name = name.valueOf()
+    name = getValue name
 
     attributes ?= {}
-    attributes = attributes.valueOf()
+    attributes = getValue attributes
     # swap argument order: text <-> attributes
     if not isObject attributes
       [text, attributes] = [attributes, text]
@@ -121,7 +121,7 @@ module.exports = class XMLDocumentCB
     if not @currentNode or @currentNode.children
       throw new Error "att() can only be used immediately after an ele() call in callback mode"
 
-    name = name.valueOf() if name?
+    name = getValue(name) if name?
 
     if isObject name # expand if object
       for own attName, attValue of name
@@ -191,8 +191,8 @@ module.exports = class XMLDocumentCB
   instruction: (target, value) ->
     @openCurrent()
 
-    target = target.valueOf() if target?
-    value = value.valueOf() if value?
+    target = getValue(target) if target?
+    value = getValue(value) if value?
 
     if Array.isArray target # expand if array
       for insTarget in target

src/XMLElement.coffee

@@ -1,4 +1,4 @@
-{ isObject, isFunction } = require './Utility'
+{ isObject, isFunction, getValue } = require './Utility'
 
 XMLNode = require './XMLNode'
 XMLAttribute = require './XMLAttribute'
@@ -59,7 +59,7 @@ module.exports = class XMLElement extends XMLNode
   # `name` attribute name
   # `value` attribute value
   attribute: (name, value) ->
-    name = name.valueOf() if name?
+    name = getValue(name) if name?
 
     if isObject name # expand if object
       for own attName, attValue of name
@@ -78,7 +78,7 @@ module.exports = class XMLElement extends XMLNode
   removeAttribute: (name) ->
     if not name?
       throw new Error "Missing attribute name"
-    name = name.valueOf()
+    name = getValue name
 
     if Array.isArray name # expand if array
       for attName in name

src/XMLNode.coffee

@@ -1,4 +1,4 @@
-{ isObject, isFunction, isEmpty } = require './Utility'
+{ isObject, isFunction, isEmpty, getValue } = require './Utility'
 
 XMLElement = null
 XMLCData = null
@@ -45,12 +45,12 @@ module.exports = class XMLNode
     lastChild = null
 
     attributes ?= {}
-    attributes = attributes.valueOf()
+    attributes = getValue attributes
     # swap argument order: text <-> attributes
     if not isObject attributes
       [text, attributes] = [attributes, text]
 
-    name = name.valueOf() if name?
+    name = getValue(name) if name?
     # expand if array
     if Array.isArray name
       lastChild = @element item for item in name
@@ -176,10 +176,10 @@ module.exports = class XMLNode
   # `attributes` an object containing name/value pairs of attributes
   # `text` element text
   node: (name, attributes, text) ->
-    name = name.valueOf() if name?
+    name = getValue(name) if name?
 
     attributes or= {}
-    attributes = attributes.valueOf()
+    attributes = getValue attributes
     # swap argument order: text <-> attributes
     if not isObject attributes
       [text, attributes] = [attributes, text]
@@ -265,8 +265,8 @@ module.exports = class XMLNode
   # `target` instruction target
   # `value` instruction value
   instruction: (target, value) ->
-    target = target.valueOf() if target?
-    value = value.valueOf() if value?
+    target = getValue(target) if target?
+    value = getValue(value) if value?
 
     if Array.isArray target # expand if array
       for insTarget in target

test/issues/176.coffee

@@ -0,0 +1,11 @@
+suite 'Tests specific to issues:', ->
+  test 'Issue #176 (valueOf fails for Object.Create(null)', ->
+    obj = Object.create(null)
+    obj.root = 'node'
+
+    eq(
+      xml(obj).end()
+      '<?xml version="1.0"?>' +
+      '<root>node</root>'
+    )
+