implemented tree-walker

src/Type/YArray.js

@@ -212,6 +212,6 @@ export default class YArray extends Type {
   _logString () {
     const left = this._left !== null ? this._left._lastId : null
     const origin = this._origin !== null ? this._origin._lastId : null
-    return `YArray(id:${logID(this._id)},start:${logID(this._start)},left:${logID(left)},origin:${logID(origin)},right:${logID(this._right)},parent:${logID(this._parent)},parentSub:${logID(this._parentSub)})`
+    return `YArray(id:${logID(this._id)},start:${logID(this._start)},left:${logID(left)},origin:${logID(origin)},right:${logID(this._right)},parent:${logID(this._parent)},parentSub:${this._parentSub})`
   }
 }

src/Type/YMap.js

@@ -109,6 +109,6 @@ export default class YMap extends Type {
   _logString () {
     const left = this._left !== null ? this._left._lastId : null
     const origin = this._origin !== null ? this._origin._lastId : null
-    return `YMap(id:${logID(this._id)},mapSize:${this._map.size},left:${logID(left)},origin:${logID(origin)},right:${logID(this._right)},parent:${logID(this._parent)},parentSub:${logID(this._parentSub)})`
+    return `YMap(id:${logID(this._id)},mapSize:${this._map.size},left:${logID(left)},origin:${logID(origin)},right:${logID(this._right)},parent:${logID(this._parent)},parentSub:${this._parentSub})`
   }
 }

src/Type/YText.js

@@ -62,6 +62,6 @@ export default class YText extends YArray {
   _logString () {
     const left = this._left !== null ? this._left._lastId : null
     const origin = this._origin !== null ? this._origin._lastId : null
-    return `YText(id:${logID(this._id)},start:${logID(this._start)},left:${logID(left)},origin:${logID(origin)},right:${logID(this._right)},parent:${logID(this._parent)},parentSub:${logID(this._parentSub)})`
+    return `YText(id:${logID(this._id)},start:${logID(this._start)},left:${logID(left)},origin:${logID(origin)},right:${logID(this._right)},parent:${logID(this._parent)},parentSub:${this._parentSub})`
   }
 }

src/Type/y-xml/YXmlFragment.js

@@ -33,6 +33,54 @@ function domToYXml (parent, doms) {
   return types
 }
 
+class YXmlTreeWalker {
+  constructor (root, f) {
+    this._filter = f || (() => true)
+    this._root = root
+    this._currentNode = root
+    this._firstCall = true
+  }
+  [Symbol.iterator] () {
+    return this
+  }
+  next () {
+    let n = this._currentNode
+    if (this._firstCall) {
+      this._firstCall = false
+      if (!n._deleted && this._filter(n)) {
+        return { value: n, done: false }
+      }
+    }
+    do {
+      if (!n._deleted && n.constructor === YXmlFragment._YXmlElement && n._start !== null) {
+        // walk down in the tree
+        n = n._start
+      } else {
+        // walk right or up in the tree
+        while (n !== this._root) {
+          if (n._right !== null) {
+            n = n._right
+            break
+          }
+          n = n._parent
+        }
+        if (n === this._root) {
+          n = null
+        }
+      }
+      if (n === this._root) {
+        break
+      }
+    } while (n !== null && (n._deleted || !this._filter(n)))
+    this._currentNode = n
+    if (n === null) {
+      return { done: true }
+    } else {
+      return { value: n, done: false }
+    }
+  }
+}
+
 export default class YXmlFragment extends YArray {
   constructor () {
     super()
@@ -55,6 +103,33 @@ export default class YXmlFragment extends YArray {
       }
     }
   }
+  createTreeWalker (filter) {
+    return new YXmlTreeWalker(this, filter)
+  }
+  /**
+   * Retrieve first element that matches *query*
+   * Similar to DOM's querySelector, but only accepts a subset of its queries
+   *
+   * Query support:
+   *   - tagname
+   * TODO:
+   *   - id
+   *   - attribute
+   */
+  querySelector (query) {
+    query = query.toUpperCase()
+    const iterator = new YXmlTreeWalker(this, element => element.nodeName === query)
+    const next = iterator.next()
+    if (next.done) {
+      return null
+    } else {
+      return next.value
+    }
+  }
+  querySelectorAll (query) {
+    query = query.toUpperCase()
+    return Array.from(new YXmlTreeWalker(this, element => element.nodeName === query))
+  }
   enableSmartScrolling (scrollElement) {
     this._scrollElement = scrollElement
     this.forEach(xml => {