initial commmit

2022-10-27 08:21:03 +02:00
commit 2a21c4136e
16 changed files with 97311 additions and 0 deletions
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+//
+//  async and await
+//
+
+function resolveAfter2Seconds(x) {
+  return new Promise(resolve => {
+    setTimeout(() => {
+      resolve(x)
+    }, 2000)
+  })
+}
+
+//  with async and await
+async function add (x) {
+  let a = resolveAfter2Seconds(20)
+  let b = resolveAfter2Seconds(30)
+  return x + await a + await b
+}
+
+//  with Promise.all
+function addP (x) {
+  return Promise.all([
+    resolveAfter2Seconds(20), 
+    resolveAfter2Seconds(30)
+  ]).then(([a, b]) => x + a + b)
+}
+
+add(10).then(console.log)
+addP(10).then(console.log)
@@ -0,0 +1,17 @@
+//
+//  Example using EventEmitter
+//
+const EventEmitter = require('events')
+const door = new EventEmitter()
+
+door.on('open', (arg) => {
+  console.log('Door was opened ' + arg)
+})
+
+process.nextTick(() => {
+  console.log('next tick')
+  door.emit('open', 'async')
+})
+
+door.emit('open', 'sync')
+
@@ -0,0 +1,23 @@
+//
+// timeout vs immediate
+//
+const fs = require('fs')
+
+setTimeout(() => {
+  console.log('timeout')
+}, 0)
+
+setImmediate(() => {
+  console.log('immediate')
+})
+
+fs.readFile("immediate2.js", () => {
+  setTimeout(() => {
+    console.log('timeout from readFile callback')
+  }, 0)
+  setImmediate(() => {
+    console.log('immediate from readFile callback')
+  })
+})
+
+console.log('script started')
@@ -0,0 +1,30 @@
+<!doctype html>
+<html lang="en">
+<head>
+	<meta charset="UTF-8">
+	<title>Event Demo</title>
+	<script>
+	
+window.onload = () => {
+
+	var bibimg = document.querySelector('img')
+  bibimg.src = "https://www.zhaw.ch/storage/_processed_/b/2/"
+           + "csm_hsb-winterthur-aussenansicht-vorne_3198f01cca.jpg"
+
+	bibimg.addEventListener('load', function() {
+		alert("Image loaded")
+	})
+
+	var timestamp = Date.now() + 3000
+	while (Date.now() < timestamp) {}
+	
+}
+	
+	</script>
+</head>
+<body>
+	<div>
+		<img src="" alt="Hochschulbibliothek in Winterthur">
+	</div>
+</body>
+</html>
@@ -0,0 +1,16 @@
+//
+//  Naive asynchronous code. This doesn’t work!
+//
+let fs = require('fs')
+let timestamp = new Date().toString()
+let contents
+
+fs.writeFile('date.txt', timestamp, () => {})
+
+fs.readFile('date.txt', (err, data) => { 
+	if (err) throw err
+	contents = data
+})
+
+console.log('Comparing the contents')
+console.assert(timestamp == contents)
@@ -0,0 +1,22 @@
+//
+//  nexttick vs. immediate and timeout events
+//
+
+const fs = require('fs')
+const process = require('process')
+
+fs.readFile("nexttick.js", () => {
+  
+  setTimeout(() => {
+    console.log('timeout')
+  }, 0)
+  
+  setImmediate(() => {
+    console.log('immediate')
+  })
+  
+  process.nextTick(() => {
+    console.log('nexttick')
+  })
+
+})
@@ -0,0 +1,20 @@
+//
+//  Rejecting a promise by throwing an error in the constructor 
+//  callback or in the handler chain
+//
+
+var promise = new Promise((resolve, reject) => { 
+//	reject()
+//	throw Error('fail')
+	resolve()
+})
+
+promise
+	.then(() => console.log('step1'))
+//	.then(() => { throw Error('fail') })
+	.then(() => console.log('step2'))
+	.catch (() => console.log('catch1'))
+	.then(() => console.log('step3'))
+	.catch (() => console.log('catch2'))
+	.then(() => console.log('step4'))
+
@@ -0,0 +1,26 @@
+//
+//  Passing values in a sequence of steps
+//
+
+function step1() {
+	return Promise.resolve('ta-da!')
+}
+
+step1().then(
+	function step2(result) {
+		console.log('Step 2 received ' + result)
+		return 'Greetings from step 2'
+	})
+	.then(
+	function step3(result) {
+		console.log('Step 3 received ' + result)
+	})
+	.then(
+	function step4(result) {
+		console.log('Step 4 received ' + result)
+		return Promise.resolve('Use my fulfilled value')
+	})
+	.then(
+	function step5(result) {
+		console.log('Step 5 received ' + result)
+	})
@@ -0,0 +1,60 @@
+//
+//  One promise with multiple consumers
+//
+//  The getProfile method creates a promise that is resolved with 
+//  a mock profile. The user is then passed to navbar.showUsername() 
+//  and account.showProfile().
+//
+//  Remember that a promise serves as a placeholder for the result 
+//  of an operation. Here, the user.profilePromise is a placeholder 
+//  used by the showUsername and show Profile functions. 
+//  These functions can be safely called at anytime before or after 
+//  the profile data is available. The callbacks they use to print 
+//  the data to the console will only be invoked once the profile 
+//  is loaded.
+//
+
+var user = { 
+	profilePromise: null,
+
+	getProfile: function () {
+		if (!this.profilePromise) {
+			
+			// This code would request the profile from the server
+			var mockProfile = {
+				name: 'Samantha', 
+				subscribedToSpam: false
+			}
+
+			this.profilePromise = new Promise(function (resolve, reject) {
+				setTimeout(()=>resolve(mockProfile), 1000)
+			})
+		}
+		return this.profilePromise
+	}
+}
+
+var navbar = {
+	showUsername: function (user) {
+		user.getProfile().then(function (profile) { 
+			console.log('*** Navbar ***')
+			console.log('Name: ' + profile.name)
+		})
+	}
+}
+
+var account = {
+	showProfile: function (user) {
+		user.getProfile().then(function (profile) { 
+			console.log('*** User Profile ***')
+			console.log('Name: ' + profile.name)
+			console.log('Send lots of email? ' + profile.subscribedToSpam)
+		})
+	} 
+}
+
+navbar.showUsername(user)
+account.showProfile(user)
+
+
+
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+//
+//  Priorities in the event loop
+//
+
+Promise.resolve().then(() => console.log('promise resolved'))
+setImmediate(() => console.log('set immediate'))
+process.nextTick(() => console.log('next tick'))
+setTimeout(() => console.log('set timeout'), 0)
+
+Promise.resolve().then(() => console.log('promise1 resolved'))
+Promise.resolve().then(() => console.log('promise2 resolved'))
+Promise.resolve().then(() => {
+    console.log('promise3 resolved')
+    process.nextTick(() => console.log('next tick inside promise resolve handler'))
+})
+Promise.resolve().then(() => console.log('promise4 resolved'))
+Promise.resolve().then(() => console.log('promise5 resolved'))
+
+setImmediate(() => console.log('set immediate1'))
+setImmediate(() => console.log('set immediate2'))
+
+process.nextTick(() => console.log('next tick1'))
+process.nextTick(() => console.log('next tick2'))
+process.nextTick(() => console.log('next tick3'))
+
+setTimeout(() => console.log('set timeout'), 0)
+setImmediate(() => console.log('set immediate3'))
+setImmediate(() => console.log('set immediate4'))
@@ -0,0 +1,22 @@
+//
+//  The Promise.all() function accepts an array of promise 
+//  instances and returns a new promise which is fulfilled 
+//  once all the promises in the array are fulfilled or 
+//  rejected as soon as any of the promises in the array 
+//  are rejected.
+//
+//  The Promise.race() function accepts an array of promise 
+//  instances and is fulfilled or rejected as soon as one of 
+//  the promises in the array is fulfilled or rejected.
+//
+
+var p1 = new Promise((resolve, reject) => { 
+	setTimeout(resolve, 2000, 'first')
+})
+
+var p2 = new Promise((resolve, reject) => { 
+	setTimeout(resolve, 3000, 'second')
+})
+
+Promise.all([p1, p2]).then(console.log)
+Promise.race([p1, p2]).then(console.log)
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+//
+//  wait returns a promise that is resolved after some time
+//
+
+function wait (ms) {
+	return new Promise(resolve => setTimeout(resolve, ms))
+}
+
+wait(2000).then(() => console.log("first"))
+wait(2000).then(() => console.log("second"))
+
@@ -0,0 +1,11 @@
+Quelle für diese Datei:
+https://ourworldindata.org/world-population-growth#population-growth-by-country
+
+
+
+HINWEIS:
+
+Die Originalversion der CSV-Datei hat in der ersten Zeile einen String, welcher
+selbst Kommas enthält. Das macht das Lasen unnötig kompliziert, daher ist die
+Originalversion nun unter population_orig.csv abgelegt und eine vereinfachte
+Version ist unter population.csv zu finden.