feat(json2xml): add option ignoreNull

Author: Clément

README.md

@@ -85,11 +85,13 @@ var chars =  {
 Default values:
 ```javascript
 var options = {
-    sanitize: false
+    sanitize: false,
+    ignoreNull: false
 };
 ```
 
-`sanitize: false` is the default option to behave like previous versions
+* `sanitize: false` is the default option to behave like previous versions
+* **ignoreNull:** Ignores all null values
 
 
 (*) xml2json tranforms CDATA content to JSON, but it doesn't generate a reversible structure.

lib/json2xml.js

@@ -21,6 +21,8 @@ module.exports = function (json, options) {
 }
 
 ToXml.prototype.parse = function(obj) {
+    if (!obj) return;
+
     var self = this;
     var keys = Object.keys(obj);
     var len = keys.length;
@@ -60,7 +62,7 @@ ToXml.prototype.parse = function(obj) {
                     self.closeTag(key);
                 }
             }
-        } else if (typeof(obj[key]) == 'object') {
+        } else if (typeof(obj[key]) == 'object' && !(self.options.ignoreNull && obj[key] === null)) {
             self.openTag(key);
             self.parse(obj[key]);
             self.closeTag(key);
@@ -97,7 +99,8 @@ ToXml.prototype.completeTag = function() {
 }
 function ToXml(options) {
     var defaultOpts = {
-        sanitize: false
+        sanitize: false,
+        ignoreNull: false
     };
 
     if (options) {