diff --git a/src/Connector.js b/src/Connector.js
index b6d1f3f5..f8c76d03 100644
--- a/src/Connector.js
+++ b/src/Connector.js
@@ -132,6 +132,7 @@ export default class AbstractConnector {
         f()
       }
       this.whenSyncedListeners = []
+      this.y.emit('synced')
     }
   }
 
diff --git a/src/Type/YMap.js b/src/Type/YMap.js
index ccab1010..03cd780f 100644
--- a/src/Type/YMap.js
+++ b/src/Type/YMap.js
@@ -34,6 +34,9 @@ export default class YMap extends Type {
     }
     return map
   }
+  keys () {
+    return this._map.keys()
+  }
   delete (key) {
     this._transact((y) => {
       let c = this._map.get(key)
@@ -58,6 +61,7 @@ export default class YMap extends Type {
       let v
       if (typeof value === 'function') {
         v = new value() // eslint-disable-line new-cap
+        value = v
       } else if (value instanceof Item) {
         v = value
       } else {
diff --git a/src/Type/y-xml/YXmlElement.js b/src/Type/y-xml/YXmlElement.js
index 64eb7a6f..b38c4e64 100644
--- a/src/Type/y-xml/YXmlElement.js
+++ b/src/Type/y-xml/YXmlElement.js
@@ -11,7 +11,7 @@ export default class YXmlElement extends YXmlFragment {
     this._scrollElement = null
     if (typeof arg1 === 'string') {
       this.nodeName = arg1.toUpperCase()
-    } else if (arg1 != null && arg1.nodeType != null && arg1.nodeType === document.ELEMENT_NODE) {
+    } else if (arg1 != null && arg1.nodeType != null && arg1.nodeType === arg1.ELEMENT_NODE) {
       this.nodeName = arg1.nodeName
       this._setDom(arg1)
     } else {
diff --git a/src/Type/y-xml/YXmlFragment.js b/src/Type/y-xml/YXmlFragment.js
index ffa3f558..d1439ee5 100644
--- a/src/Type/y-xml/YXmlFragment.js
+++ b/src/Type/y-xml/YXmlFragment.js
@@ -17,9 +17,9 @@ function domToYXml (parent, doms) {
     }
     if (parent._domFilter(d, []) !== null) {
       let type
-      if (d.nodeType === document.TEXT_NODE) {
+      if (d.nodeType === d.TEXT_NODE) {
         type = new YXmlText(d)
-      } else if (d.nodeType === document.ELEMENT_NODE) {
+      } else if (d.nodeType === d.ELEMENT_NODE) {
         type = new YXmlFragment._YXmlElement(d, parent._domFilter)
       } else {
         throw new Error('Unsupported node!')
diff --git a/src/Type/y-xml/YXmlText.js b/src/Type/y-xml/YXmlText.js
index e8c48c18..c3d3f5db 100644
--- a/src/Type/y-xml/YXmlText.js
+++ b/src/Type/y-xml/YXmlText.js
@@ -5,7 +5,7 @@ export default class YXmlText extends YText {
     let dom = null
     let initialText = null
     if (arg1 != null) {
-      if (arg1.nodeType === document.TEXT_NODE) {
+      if (arg1.nodeType != null && arg1.nodeType === arg1.TEXT_NODE) {
         dom = arg1
         initialText = dom.nodeValue
       } else if (typeof arg1 === 'string') {
diff --git a/src/Util/NamedEventHandler.js b/src/Util/NamedEventHandler.js
index cbb07c9d..8ba9d7aa 100644
--- a/src/Util/NamedEventHandler.js
+++ b/src/Util/NamedEventHandler.js
@@ -2,13 +2,24 @@ export default class NamedEventHandler {
   constructor () {
     this._eventListener = new Map()
   }
-  on (name, f) {
-    let fSet = this._eventListener.get(name)
-    if (fSet === undefined) {
-      fSet = new Set()
-      this._eventListener.set(name, fSet)
+  _getListener (name) {
+    let listeners = this._eventListener.get(name)
+    if (listeners === undefined) {
+      listeners = {
+        once: new Set(),
+        on: new Set()
+      }
+      this._eventListener.set(name, listeners)
     }
-    fSet.add(f)
+    return listeners
+  }
+  once (name, f) {
+    let listeners = this._getListener(name)
+    listeners.once.add(f)
+  }
+  on (name, f) {
+    let listeners = this._getListener(name)
+    listeners.on.add(f)
   }
   off (name, f) {
     if (name == null || f == null) {
@@ -22,7 +33,9 @@ export default class NamedEventHandler {
   emit (name, ...args) {
     const listener = this._eventListener.get(name)
     if (listener !== undefined) {
-      listener.forEach(f => f.apply(null, args))
+      listener.on.forEach(f => f.apply(null, args))
+      listener.once.forEach(f => f.apply(null, args))
+      listener.once = new Set()
     } else if (name === 'error') {
       console.error(args[0])
     }
diff --git a/src/Y.js b/src/Y.js
index 746aeda9..045dc101 100644
--- a/src/Y.js
+++ b/src/Y.js
@@ -24,6 +24,7 @@ export default class Y extends NamedEventHandler {
     super()
     this._opts = opts
     this.userID = opts._userID != null ? opts._userID : generateUserID()
+    this.share = {}
     this.ds = new DeleteStore(this)
     this.os = new OperationStore(this)
     this.ss = new StateStore(this)
@@ -71,7 +72,7 @@ export default class Y extends NamedEventHandler {
   get room () {
     return this._opts.connector.room
   }
-  get (name, TypeConstructor) {
+  define (name, TypeConstructor) {
     let id = new RootID(name, TypeConstructor)
     let type = this.os.get(id)
     if (type === null) {
@@ -79,9 +80,18 @@ export default class Y extends NamedEventHandler {
       type._id = id
       type._parent = this
       type._integrate(this)
+      if (this.share[name] !== undefined) {
+        throw new Error('Type is already defined with a different constructor!')
+      }
+    }
+    if (this.share[name] === undefined) {
+      this.share[name] = type
     }
     return type
   }
+  get (name) {
+    return this.share[name]
+  }
   disconnect () {
     if (this.connected) {
       this.connected = false
@@ -109,6 +119,13 @@ export default class Y extends NamedEventHandler {
     this.ds = null
     this.ss = null
   }
+  whenSynced () {
+    return new Promise(resolve => {
+      this.once('synced', () => {
+        resolve()
+      })
+    })
+  }
 }
 
 Y.extend = function extendYjs () {