add type definition file for node-observer (#40450)

* add type definition file for node-observer

* remove unnecessary comment in index.d.ts

* fix test errors

* fix test errors

types/node-observer/index.d.ts

@@ -0,0 +1,32 @@
+// Type definitions for node-observer 0.4
+// Project: https://github.com/hormander/node-observer
+// Definitions by: wjchi <https://github.com/CwjXFH>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+
+export = observer;
+
+declare class Observer {
+    private subscribers: object[];
+    /**
+     * subscirpt event
+     * @param targetObj objects that subscribe to events
+     * @param eventName the event name
+     * @param callback callback function executed when an event is fired
+     */
+    subscribe(targetObj: object, eventName: string, callback: any): void;
+    /**
+     * unsubscript event
+     * @param targetObj objects that subscribe to events
+     * @param eventName the event name
+     */
+    unsubscribe(targetObj: object, eventName: string): void;
+    /**
+     * triggering event
+     * @param targetObj objects that subscribe to events
+     * @param eventName the event name
+     * @param data passed to the callback function when the event is fired
+     */
+    send(targetObj: object, eventName: string, data: any): void;
+}
+
+declare let observer: Observer;

types/node-observer/node-observer-tests.ts

@@ -0,0 +1,16 @@
+import observer = require("node-observer");
+
+class Demo {
+    sayHello(msg: string) {
+        console.log(`hello ${msg}`);
+    }
+}
+
+const obj = new Demo();
+
+for (let i = 0; i < 3; i++) {
+    observer.subscribe(obj, "hello", obj.sayHello);
+}
+observer.unsubscribe(obj, "hello");
+
+observer.send(obj, "hello", "sent event");

types/node-observer/tsconfig.json

@@ -0,0 +1,24 @@
+{
+    "compilerOptions": {
+        "module": "commonjs",
+        "lib": [
+            "es6",
+            "dom"
+        ],
+        "noImplicitAny": true,
+        "noImplicitThis": true,
+        "strictNullChecks": true,
+        "strictFunctionTypes": true,
+        "baseUrl": "../",
+        "typeRoots": [
+            "../"
+        ],
+        "types": [],
+        "noEmit": true,
+        "forceConsistentCasingInFileNames": true
+    },
+    "files": [
+        "index.d.ts",
+        "node-observer-tests.ts"
+    ]
+}

types/node-observer/tslint.json

@@ -0,0 +1,3 @@
+{
+    "extends": "dtslint/dt.json"
+}