feat(nodes.js): add forEach method to allow iterating over nodes

lib/nodes.js

@@ -1,5 +1,7 @@
 'use strict'
 
+const Node = require('./node')
+
 /**
  * @class
  * @memberof node-html-light
@@ -55,6 +57,47 @@ class Nodes {
 
         return result
     }
+
+    /**
+      * Executes the callback function for every wrapped element and (optionally) for every wrapped elements children
+      * @param {Function} callback the callback to be invoked for every element
+      * @param {Boolean} [recursive=false] recursive flag to indicate if callback should be invoked for child elements, too
+      */
+    forEach(callback, recursive) {
+        this._elements.forEach((element) => {
+
+            // iterating recursively we have to wrap the parser nodes with our node implementation
+            if (!(element instanceof Node)) {
+                element = Node.create(element)
+            }
+
+            const type = element.get().type
+            const whitespace = this._isWhitespace(element)
+            if ( type === Node.TYPE_TAG || type === Node.TYPE_COMMENT || !whitespace) {
+                callback(element)
+            }
+
+            if (recursive) {
+                const children = element.get().children
+                if (children && children.length) {
+                    new Nodes(children).forEach(callback, recursive)
+                }
+            }
+        })
+    }
+
+    _isWhitespace(element) {
+        const type = element.get().type
+
+        if (type === 'text') {
+            const text = element.get().data
+            if (/^[\s\\n\\r]*$/.test(text)) {
+                return true
+            }
+        }
+
+        return false
+    }
 }
 
 module.exports = Nodes