1 files changed, 98 insertions, 0 deletions
diff --git a/src/plugins/imagery/lib/eventHelpers.js b/src/plugins/imagery/lib/eventHelpers.js
new file mode 100644
index 000000000..d4bbac4c7
--- /dev/null
+++ b/src/plugins/imagery/lib/eventHelpers.js
@@ -0,0 +1,98 @@
+/*****************************************************************************
+ * Open MCT, Copyright (c) 2014-2021, United States Government
+ * as represented by the Administrator of the National Aeronautics and Space
+ * Administration. All rights reserved.
+ *
+ * Open MCT is licensed under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * http://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ * Open MCT includes source code licensed under additional open source
+ * licenses. See the Open Source Licenses file (LICENSES.md) included with
+ * this source code distribution or the Licensing information page available
+ * at runtime from the About dialog for additional information.
+ *****************************************************************************/
+
+define([], function () {
+    const helperFunctions = {
+        listenTo: function (object, event, callback, context) {
+            if (!this._listeningTo) {
+                this._listeningTo = [];
+            }
+
+            const listener = {
+                object: object,
+                event: event,
+                callback: callback,
+                context: context,
+                _cb: context ? callback.bind(context) : callback
+            };
+            if (object.$watch && event.indexOf('change:') === 0) {
+                const scopePath = event.replace('change:', '');
+                listener.unlisten = object.$watch(scopePath, listener._cb, true);
+            } else if (object.$on) {
+                listener.unlisten = object.$on(event, listener._cb);
+            } else if (object.addEventListener) {
+                object.addEventListener(event, listener._cb);
+            } else {
+                object.on(event, listener._cb);
+            }
+
+            this._listeningTo.push(listener);
+        },
+
+        stopListening: function (object, event, callback, context) {
+            if (!this._listeningTo) {
+                this._listeningTo = [];
+            }
+
+            this._listeningTo.filter(function (listener) {
+                if (object && object !== listener.object) {
+                    return false;
+                }
+
+                if (event && event !== listener.event) {
+                    return false;
+                }
+
+                if (callback && callback !== listener.callback) {
+                    return false;
+                }
+
+                if (context && context !== listener.context) {
+                    return false;
+                }
+
+                return true;
+            })
+                .map(function (listener) {
+                    if (listener.unlisten) {
+                        listener.unlisten();
+                    } else if (listener.object.removeEventListener) {
+                        listener.object.removeEventListener(listener.event, listener._cb);
+                    } else {
+                        listener.object.off(listener.event, listener._cb);
+                    }
+
+                    return listener;
+                })
+                .forEach(function (listener) {
+                    this._listeningTo.splice(this._listeningTo.indexOf(listener), 1);
+                }, this);
+        },
+
+        extend: function (object) {
+            object.listenTo = helperFunctions.listenTo;
+            object.stopListening = helperFunctions.stopListening;
+        }
+    };
+
+    return helperFunctions;
+});