Adding support for reading the last value.

package-lock.json

@@ -1,13 +1,13 @@
 {
   "name": "@hibas123/utils",
-  "version": "2.1.0",
+  "version": "2.1.1",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
     "typescript": {
-      "version": "3.4.5",
-      "resolved": "https://registry.npmjs.org/typescript/-/typescript-3.4.5.tgz",
-      "integrity": "sha512-YycBxUb49UUhdNMU5aJ7z5Ej2XGmaIBL0x34vZ82fn3hGvD+bgrMrVDpatgz2f7YxUMJxMkbWxJZeAvDxVe7Vw==",
+      "version": "3.5.3",
+      "resolved": "https://registry.npmjs.org/typescript/-/typescript-3.5.3.tgz",
+      "integrity": "sha512-ACzBtm/PhXBDId6a6sDJfroT2pOWt/oOnk4/dElG5G33ZL776N3Y6/6bKZJBFpd+b05F3Ct9qDjMeJmRWtE2/g==",
       "dev": true
     }
   }

package.json

@@ -16,7 +16,7 @@
     "type": "git"
   },
   "devDependencies": {
-    "typescript": "^3.4.5"
+    "typescript": "^3.5.3"
   },
   "files": [
     "src/",
@@ -25,4 +25,4 @@
     "readme.md"
   ],
   "private": false
-}
+}

src/observable.ts

@@ -20,6 +20,7 @@ export type ObservableInterface<T> = {
 };
 
 const ClosedSymbol = Symbol("Observable Closed");
+const LastValueSymbol = Symbol("Observable LastValue");
 
 export default class Observable<T = any> {
    private subscriber: ObserverCallback<T>[] = [];
@@ -30,12 +31,22 @@ export default class Observable<T = any> {
    // Use symbol to make sure this property cannot be changed from the outside
    private [ClosedSymbol] = false;
 
+   private [LastValueSymbol]: T | undefined = undefined;
+
+   get lastValue() {
+      return this[LastValueSymbol];
+   }
+
    get closed() {
       return this[ClosedSymbol];
    }
 
    constructor(private collect_intervall: number = 100) { }
 
+   /**
+    * Subscribe to changes
+    * @param callback Callback called once a value is available
+    */
    subscribe(callback: ObserverCallback<T>) {
       if (this[ClosedSymbol])
          throw new Error("Observable is closed!");
@@ -45,6 +56,10 @@ export default class Observable<T = any> {
          this.subscriber.push(callback)
    }
 
+   /**
+    * Unsubscribe specified callback. After that, it will be discarded.
+    * @param callback The callback originally subscribed
+    */
    unsubscribe(callback: ObserverCallback<T> | ObserverCallbackCollect<T>) {
       if (this[ClosedSymbol])
          return;
@@ -59,6 +74,10 @@ export default class Observable<T = any> {
       }
    }
 
+   /**
+    * Subscribe for a collection of changes
+    * @param callback Callback called once a or some values are available.
+    */
    subscribeCollect(callback: ObserverCallbackCollect<T>) {
       if (this[ClosedSymbol])
          throw new Error("Observable is closed!");
@@ -89,7 +108,9 @@ export default class Observable<T = any> {
     */
    send(data: T) {
       if (this[ClosedSymbol])
-         throw new Error("Observable is closed!")
+         throw new Error("Observable is closed!");
+         
+      this[LastValueSymbol] = data;
       this.subscriber.forEach(e => e(data));
       this.events.push(data);
       if (!this.timeout) {