added promises exercise

express-examples/express2.js

@@ -3,6 +3,8 @@
 const express = require('express');
 const app = express();
 
+app.use(express.static('./'));
+
 app.get('/api/contacts', getContacts);
 app.get('/api/contacts/:id', getContact);
 

promises.js

@@ -0,0 +1,30 @@
+
+var promise = Promise.resolve(1); // vs. Promise.reject(new Error('failed'));
+
+promise.then(result => {
+    console.log('1: ' + result);
+
+    return getData(result);
+}).then(result => {
+    console.log('2: ' + result);
+
+    return 1;
+}).then(result => {
+    // no return
+}).then(result => {
+    throw new Error('sth bad happened');
+}).then(result => {
+    // skipped
+}).catch(error => {
+    // process error
+    // throw error
+    // return 1
+}).then(result => {
+    // executed if catch
+    // does not throw
+});
+
+function getData() {
+    return Promise.resolve('some data');
+    // return Promise.reject(new Error('no data'));
+}