restructuring the project

src/utils/YEvent.js

@@ -0,0 +1,39 @@
+/**
+ * @module utils
+ */
+
+/**
+ * YEvent describes the changes on a YType.
+ */
+export class YEvent {
+  /**
+   * @param {Type} target The changed type.
+   */
+  constructor (target) {
+    /**
+     * The type on which this event was created on.
+     * @type {Type}
+     */
+    this.target = target
+    /**
+     * The current target on which the observe callback is called.
+     * @type {Type}
+     */
+    this.currentTarget = target
+  }
+
+  /**
+   * Computes the path from `y` to the changed type.
+   *
+   * The following property holds:
+   * @example
+   *   let type = y
+   *   event.path.forEach(dir => {
+   *     type = type.get(dir)
+   *   })
+   *   type === event.target // => true
+   */
+  get path () {
+    return this.currentTarget.getPathTo(this.target)
+  }
+}