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WBE_Praktikum_5
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schrom01 2022-10-27 08:21:03 +02:00
commit 2a21c4136e
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29
code/async/async-await.js Normal file
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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)

17
code/async/emitter.js Normal file
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//
// 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')

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code/async/immediate.js Normal file
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//
// 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')

30
code/async/load_event.html Normal file
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<!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>

16
code/async/naive_async.js Normal file
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//
// 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)

22
code/async/nexttick.js Normal file
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//
// 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')
})
})

20
code/async/promise-chain.js Normal file
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//
// 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'))

26
code/async/promise-data.js Normal file
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//
// 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)
})

60
code/async/promise-demo.js Normal file
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//
// 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'))

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code/async/promise-race-all.js Normal file
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//
// 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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code/async/promise-wait.js Normal file
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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"))

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code/csv/README.txt Normal file
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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.

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