react-workshop/es6-und-typescript.html at master · reactbuch/react-workshop · GitHub

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<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8" />

    <title>React Workshop</title>

    <meta name="apple-mobile-web-app-capable" content="yes" />
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        background: rgb(252, 220, 185) url("ai/es6-icon.png") no-repeat right bottom;
      }
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  </head>

  <body>
    <div class="reveal">
      <!-- Any section element inside of this container is displayed as a slide -->
      <div class="slides">
        <section data-state="exkurs">
          <h3>Hintergrund</h3>
          <h2>ES6 Features</h2>
        </section>

        <section data-state="exkurs">
          <h3>ES6: Klassen</h3>
          <pre><code class="javascript" contenteditable>class Person {
    constructor(name) {
        this._name = name;
    }
    getName() {
        return this._name;
    }
}
class Programmer extends Person {
    constructor(name, language) {
        super(name);
        this.language = language;
    }
    code() {
        return `${this.getName()} codes in ${this.language}`;
    }
}</code></pre>
          <pre class="fragment"><code class="javascript" contenteditable>const programmer = new Programmer('Erna', 'JavaScript');
console.log(programmer.code());
console.log(programmer instanceof Programmer); // true
console.log(programmer instanceof Person); // true</code></pre>
        </section>
        <section data-state="exkurs"><h2>ES6: Module, Importe und Exporte</h2></section>
        <section data-state="exkurs">
          <h3>ES6: Export einer einzigen Klasse</h3>
          <pre><code class="javascript" contenteditable>// Person.js
  class Person {
    // ...
  }
  export default Person;
     </code></pre>
          <pre><code class="javascript" contenteditable>// Person.js

  // in einer Zeile zusammengefasst
  export default class Person {
    // ...
  }
     </code></pre>
        </section>
        <section data-state="exkurs">
          <h3>ES6: Import</h3>
          <pre><code class="javascript" contenteditable>// Programmer.js
  import Person from './Person';

  export default class Programmer extends Person {
    // ...
  }
     </code></pre>
        </section>
        <section data-state="exkurs">
          <h3>ES6: Benannte Exporte</h3>
          <pre><code class="javascript" contenteditable data-trim>// util.js
  export function displayInPage(text) {
      document.body.innerHTML +=
          `${text}<br>` ;
  }

  export showInfo = msg => window.alert(`Wichtige Info: ${msg}`);

  // or
  function displayInPage(text) { . . . }

  const showInfo = ...;

  // specify exports
  export { displayInPage, showInfo };
     </code></pre>
          <pre class="fragment"><code class="javascript" contenteditable data-trim>import {displayInPage} from "./util";
  displayInPage('Hello, World');
     </code></pre>
          <!--
            <pre class="fragment"><code class="javascript" contenteditable data-trim>import {displayInPage as display} from "./util";
          -->
          <!-- display('Hello, World'); -->
          <!-- </code></pre> -->
          <!-- <pre class="fragment"><code class="javascript" contenteditable data-trim>import * as util from "./util"; -->
          <!-- util.displayInPage('Hello, World'); -->
          <!-- </code></pre> -->
        </section>
        <section data-state="exkurs">
          <h3>ES6: Arrow Functions</h3>
          <pre><code class="javascript" contenteditable>const displayInPage = (text) => {
   return document.body.innerHTML +=
       `${text}<br>`;
};</code></pre>
          <pre
            class="fragment"
          ><code class="javascript" contenteditable>// Klammern können weggelassen werden, genau ein Parameter
// ebenso die geschweiften Klassen, wenn nur ein Statement:
const displayInPage = text => document.body.innerHTML += `${text}<br>`;
</code></pre>
        </section>
        <section data-state="exkurs">
          <h3>ES6: Template Strings</h3>
          <p>Template Strings werden in Backticks (``) geschrieben und können Ausdrücke (in <code>${}</code>) enthalten:</p>

          <pre><code class="javascript" contenteditable>const name = "Susi";
const greeting = `Hello, ${name}`; // Hello, Susi

const four = `Two and two is: ${2+2}` // Two and two is: 4

const time = `The time is: ${new Date()}`); // The time is: ...
            </code></pre>
        </section>

        <section data-state="exkurs">
          <h3>ES6: Erweiterte Objekt-Literale</h3>
          <pre><code class="javascript" contenteditable>

// ES5:
const firstName = 'Klaus';
const person = {
    firstName: firstName
};
console.log(person.firstName); // Klaus

// ES6:
const firstName = 'Klaus';
const person = {
    firstName
};
console.log(person.firstName); // Klaus
   </code></pre>
        </section>

        <!-- <section> -->
        <!-- <h2>Neuerungen und Verbesserungen in ES6</h2> -->
        <!-- </section> -->

        <!-- <section> -->
        <!-- <h3>Tagged Template Literals</h3> -->
        <!-- <p><a target="_blank" href="http://exploringjs.com/es6/ch_template-literals.html#_tagged-templates"> -->
        <!-- Mini-DSLs: Template-Literals mit tag -->
        <!-- </a> -->
        <!-- </p> -->

        <!-- <pre class="fragment"><code class="javascript" contenteditable>function tag(strings, ...values) { -->
        <!-- console.log(strings); -->
        <!-- //[ '', ' codes in ', '.' ] -->
        <!-- console.log(values); -->
        <!-- //[ 'Oma', 'Haskell' ] -->
        <!-- return 'whatever you want'; -->
        <!-- } -->
        <!-- </code></pre> -->

        <!-- <pre><code class="javascript" contenteditable>const expanded = tag`${person} codes in ${language}.`; -->
        <!-- console.log(expanded); -->
        <!-- //whatever you want -->
        <!-- </code></pre> -->

        <!-- </section> -->

        <section data-state="exkurs">
          <h3>ES6: Destructuring von Objekten</h3>
          <pre><code class="javascript" contenteditable>const person = {
  fistName: 'Klaus',
  lastName: 'Mueller',
  age: 42
};</code></pre>
          <pre class="fragment"><code class="javascript" contenteditable>const {firstName, age, notThere} = person;

console.log(firstName); // Klaus
console.log(age); // 42
console.log(notThere); // undefined
</code></pre>
          <pre class="fragment"><code class="javascript" contenteditable>function someFunction({firstName, age, notThere}) {
  console.log(firstName); // Klaus
  console.log(age); // 42
  console.log(notThere); // undefined
}

someFunction(person);
</code></pre>
        </section>

        <section data-state="exkurs"><h2>ES6: Promises</h2></section>
        <section data-state="exkurs">
          <h3>Ein Promise ist ein Versprechen auf einen Wert</h3>
          <h4 class="fragment">Wird evtl. erst in der Zukunft eingelöst</h4>
        </section>

        <section data-state="exkurs">
          <h3>Verkettete Ausführung</h3>
          <pre><code class="javascript" contenteditable>const promise = . . .;
</code></pre>
          <pre class="fragment"><code class="javascript" contenteditable>// then returns a new promise
const promise2 = promise.then(value => `${value} plus stuff`);</code></pre>
          <pre class="fragment"><code class="javascript" contenteditable>promise2.then(value => console.log(value));
// Output after 1 second: Result from promise plus stuff
</code></pre>
        </section>
        <section data-state="exkurs">
          <h3>Fehler führen zum Abbruch der Chain</h3>
          <h4>Allerdings <b>muss</b> man etwas tun, um das mitzubekommen: catch()</h4>
        </section>

        <section data-state="exkurs">
          <h3>Catch-Klausel im Erfolgsfall</h3>
          <pre><code class="javascript" contenteditable>Promise
    // creates and directly resolves promise
    .resolve('Result from promise')
    .then(x => {
        // this will be printed
        console.log(x);
    })
    .then(() => {
        console.log('This will be printed');
    })
    // this will NOT be printed as no error occured
    .catch(e => console.log('error: ', e))

// Output:
// Result from promise
// This will be printed</code></pre>
        </section>
        <section data-state="exkurs">
          <h3>Catch-Klausel im Fehlerfall</h3>
          <pre><code class="javascript" contenteditable>Promise
    // creates and directly resolves promise
    .resolve('Result from promise')
    .then(x => {
        // this will be printed
        console.log(x);
        throw new Error('Something went wrong');
    })
    .then(() => {
        console.log('This will NOT be printed');
    })
    // this will be printed
    .catch(e => console.log('error: ', e))

// Output:
// Result from promise
// error:  [Error: Something went wrong]</code></pre>
        </section>

        <section data-state="exkurs">
          <h3>Alternative zu Promises</h3>
          <h2>async / await</h2>
          <p>Erlauben es, asynchronen Code "linear" hinzuschreiben</p>
          <ul class="fragment">
            <li>Seit ECMASCript 2017 Standard</li>
            <li>Babel und TypeScript können nach ES5 compilieren</li>
            <li>Promise Polyfill für ältere Browser verwenden</li>
          </ul>
        </section>

        <section data-state="exkurs">
          <h3>async / await</h3>
          <ul>
            <li class="fragment"><code>aync</code> definiert "async functions"</li>
            <li class="fragment">
              <code>aync</code> functions liefern&nbsp; <b>immer</b> ein Promise zurück:
              <pre><code class="javascript" contenteditable data-trim>
async function greet(name) {
  return `Hello, ${name}`;
}

const greeting = greet('Klaus');

// greeting ist ein Promise!
console.log(greeting instanceof Promise); // => true
console.log(greeting) // => Promise {&lt;resolved>: "Hello, Klaus"}
                </code></pre>
            </li>
            <li class="fragment">
              <code>aync</code> function als Fat Arrow function:
              <pre><code class="javascript" contenteditable data-trim>
const greet = async (name) => `Hello, ${name}`;

const greeting = greet('Klaus');

// greeting ist ein Promise!
console.log(greeting instanceof Promise); // => true
console.log(greeting) // => Promise {&lt;resolved>: "Hello, Klaus"}
                  </code></pre>
            </li>
            <li class="fragment">Nur in <b>async functions</b> kann <code>await</code> verwendet werden!</li>
          </ul>
        </section>

        <section data-state="exkurs">
          <h3>async / await</h3>
          <p><code>await</code> wartet auf erfüllte Promises</p>
          <pre class="fragment"><code class="javascript" contenteditable data-trim>
async function greet(name) {
  return `Hello, ${name}`;
}

// oder:
function greet(name) { return new Promise(...); }

async function sayWhat(name) {
  const greeting = await greet(name);

  // ...Achtung! Hier zwischen kann Zeit vergehen...

  // greeting ist ein String!
  console.log(greeting); // => Hello, ...
}
                  </code></pre>
        </section>
        <section data-state="exkurs">
          <h3>async / await</h3>
          <p>
            Statt <code>then</code> bzw <code>catch</code> werden mehrere <code>await</code> Statements bzw Exception Handling
            verwendet:
          </p>
          <pre class="fragment"><code class="javascript" contenteditable data-trim>
// Liefert ein Promise zurück
async function loadUser(username) { . . . };
async function loadProfileDate(userId) { . . .};

async function loadData() {
  try {
    const user = loadUser('klaus');
    const profile = loadProfileData(user.userId);
  } catch (e) {
    console.error("Something failed")
  }
}
                    </code></pre>
        </section>

        <section data-state="exkurs">
          <h3>async / await</h3>
          <p>Auf mehrere Promises parallel warten #2</p>
          <p>Mit <em>Array Destructuring</em></p>
          <pre class="fragment"><code class="javascript" contenteditable data-trim>
  // Liefert ein Promise zurück
  async function loadUser(userId) { . . . };
  async function loadProfileDate(userId) { . . .};

  async function loadData(userId) {
    try {
      const [user, profileData] = await Promise.all([
        loadUser(userId),
        loadProfileData(userId)
      ]);

      . . .
    } catch (e) {

      // wenn mind einer Aufrufe schief geht
      console.error("Something failed")
    }
  }
                        </code></pre>
        </section>

        <section id="t4a">
          <h2>Hintergrund: TypeScript</h2>
          <p>
            <em>TypeScript is a superset of JavaScript that compiles to plain JavaScript </em>(
            <a href="http://www.typescriptlang.org/" target="_blank">http://www.typescriptlang.org/</a>)
          </p>
          <ul>
            <li>Erweitert JavaScript um ein Typen System</li>
            <li>Jeder gültige JavaScript Code ist auch gültiger TypeScript Code</li>
            <li>Mittels des TypeScript Compilers wird aus TS Code JavaScript Code</li>
            <li>Entwickelt von Microsoft</li>
            <li>Unterstützung in vielen IDEs (z.B. Anzeige von Fehlern, Refactoring, ...)</li>
          </ul>
        </section>

        <section>
          <h3>Wichtige Unterschiede zu Java/C#</h3>
          <ul>
            <li>
              Typ-Informationen sind nach dem compilieren weg (keine Reflection API etc)
              <ul>
                <li>Das gilt auch für Sichtbarkeiten und readonly Felder</li>
              </ul>
            </li>
            <li>Es wird auch JavaScript-Code erzeugt, selbst wenn es einen Compile-Fehler gibt</li>
            <li>Im Gegensatz zu Java/C# sind bei TypeScript zwei Typen kompatibel, sofern sie <b>dieselbe Struktur</b> haben</li>
          </ul>
        </section>

        <section>
          <h3>TypeScript Grundlagen</h3>
          <p>Typ-Angaben werden hinter einen Bezeichner geschrieben</p>
          <pre class="fragment"><code class="typescript line-numbers" contenteditable data-trim>
// Variablen können Typ-Informationen bekommen
let foo: string;
foo = 'yo';
// Error: number: This type is incompatible with string
foo = 10;
               </code></pre>
          <pre class="fragment"><code class="typescript line-numbers" contenteditable data-trim>
// Funktionen
function sayIt(what: string): string {
  return `Saying: ${what}`;
}

sayIt('Klaus'); // ok
sayIt(10); // error
</code></pre>

          <pre class="fragment"><code class="typescript line-numbers" contenteditable data-trim>
// Arrow Funktionen
const sayIt = (what: string): string => `Saying: ${what}`;

sayIt('Moin');
sayIt(123); // Error: Argument of type '123' is not assignable
            // to parameter of type 'string'.
</code></pre>
        </section>

        <section>
          <h2>Eingebaute Typen</h2>
          <pre class="fragment"><code class="typescript line-numbers" contenteditable data-trim>
// string
let city: string = 'Hamburg';

// boolean
let isDone: boolean = false;

// number
let theAnswer: number = 42;

// array (note the [])
let cities: string[] = ['Hamburg', 'Barcelona'];
// alternative:
let languages: Array&lt;string> = ['JavaScript', 'TypeScript'];

// any
let theUnknown: any = 'Who cares';
theUnknown = 666; // ok
theUnknown = true; // ok
let a: number = theUnknown; // ok

// void
function log(s: string): void { /* ... */ }
            </code></pre>
        </section>
        <section>
          <h2>Typen können abgeleitet (inferred) werden</h2>
          <pre class="fragment"><code class="typescript line-numbers" contenteditable data-trim>
let city = 'Hamburg'; // city ist ein String

city = 42;
// Fehler: [ts] Type '42' is not assignable to type 'string'.
</code></pre>
          <pre class="fragment"><code class="typescript line-numbers" contenteditable data-trim>
// Explizite Angabe eines Types (parameter)
// und abgeleiteter Typ (Return Type der Funktion)

function sayIt(what: string) {
  return `Saying: ${what}`;
}

const said: string = sayIt('Hello TypeScript'); // ok
const saidItWrong: number = sayIt('Hello TypeScript'); // error!


</code></pre>
        </section>
        <section>
          <h2>Strict Mode</h2>
          <ul>
            <li><b>strict</b>: seit TypeScript 2.3</li>
            <li>
              Shortcut u.a. für:
              <ul>
                <li><b>noImplicitAny</b>: <code>any</code> muss explizit hingeschrieben werden</li>
                <li><b>strictNullChecks</b>: Null muss explizit erlaubt werden (z.B. bei Rückgabewerten)</li>
              </ul>
            </li>
            <li>Empfehlung: für neue Projekte einschalten, sonst Schrittweise</li>
          </ul>
          <p>
            <a href="https://www.typescriptlang.org/docs/handbook/compiler-options.html" target="_blank"
              >https://www.typescriptlang.org/docs/handbook/compiler-options.html</a
            >
          </p>
        </section>
        <section>
          <h2>Type Check ausschalten</h2>
          <p>Mit <code>@ts-ignore</code> (als Kommentar) kann wird die Überprüfung der nächsten Zeile ausgeschaltet:</p>
          <pre><code class="typescript line-numbers" contenteditable data-trim>
let city:string = "Hamburg";

city = 20259; // error: [ts] Type '20259' is not assignable to type 'string'.

// @ts-ignore
city = 20259; // ok
</code></pre>
          <p class="fragment">Nützlich in corner cases, die nur schwer mit TypeScript abbildbar sind oder bei Migration</p>
        </section>
        <section>
          <h2>null und undefined</h2>
          <div class="fragment">
            <p><code>null</code> muss explizit zugelassen werden <em>(strictNullChecks</em>):</p>
            <pre><code class="typescript line-numbers" contenteditable data-trim>
let city:string = null; //Type 'null' is not assignable to type 'string'.

let optionalCity:string|null = null; // OK
            </code></pre>
          </div>
          <div class="fragment">
            <p>Optionale Parameter können mit ? gekennzeichnet werden (erlauben dann auch <code>undefined</code>)</p>
            <pre class="fragment"><code class="typescript line-numbers" contenteditable data-trim>
function greet(name: string, greeting?: string) {
  console.log(`${greeting || 'Hello'}, {name}`);
}

greet('Susi', 'Moin')// Moin, Susi

// 2. Parameter ist optional:
greet('Klaus'); // Hello, Klaus

greet('Peter', null); // Argument of type 'null' is not assignable
                      // to parameter of type 'string | undefined'.
            </code></pre>
          </div>
        </section>

        <section>
          <h2>Klassen</h2>
          <pre class="fragment"><code class="typescript line-numbers" contenteditable data-trim>
class Sayer {
  what: string; // Typ-Angabe für Felder ist erforderlich

  constructor(what: string) { // Typ-Angabe für Parameter ist erforderlich
    this.what = what;
  }

  // Angabe des Return-Types optional
  sayIt(): string {
    return `Saying: ${this.what}`;
  }
}

</code></pre>
        </section>

        <section>
          <h2>Klassen (Sichtbarkeiten)</h2>
          <pre class="fragment"><code class="typescript line-numbers" contenteditable data-trim>
class Sayer {
  // Erlaubte Sichtbarkeiten: private | protected | public
  private what: string;

  constructor(what: string) {
    this.what = what;
  }

  sayIt(): string {
    return `Saying: ${this.what}`;
  }
}

const sayer = new Sayer("Susi");
sayer.what = ""; // ERROR: Property 'greeting' is private

</code></pre>
        </section>
        <section>
          <h2>Klassen (Parameter Properties)</h2>
          <pre class="fragment"><code class="typescript line-numbers" contenteditable data-trim>
class Sayer {
  // identisch zu vorherigem Beispiel
  constructor(private what: string) {
  }

  sayIt(): string {
    return `Saying: ${this.what}`;
  }
}
</code></pre>
        </section>
        <section>
          <h2>Klassen (readonly Felder)</h2>
          <pre class="fragment"><code class="typescript line-numbers" contenteditable data-trim>
class Sayer {

  readonly what: string;

  // Alternativ:
  constructor(readonly public what: string) {
  }

  setWhat(newWhat: string) {
    this.what = newWhat; // ERR Cannot assign to 'what'
                         // because it is a read-only property.
  }
}
</code></pre>
        </section>
        <section>
          <h2>Eigene Typen</h2>
          <p>Mit <code>interface</code> können eigene Typen defniert werden:</p>

          <pre><code data-trim contenteditable class="line-numbers typescript" data-leftpad>
// Komplexer Typ
interface Person {
	name: string; // Pflicht
	livesIn?: string; // Optional
}

const susi: Person = { // OK
	name: 'Klaus',
	livesIn: 'Hamburg'
};
const klaus: Person = { // OK (livesIn ist optional)
	name: 'Klaus'
}

const helmut: Person = {} // Error: Property 'name' is missing

const lukas: Person = {
	name: 'Lukas',
	profession: 'Lokführer'
} // Error: 'profession' does not exist in type 'Person'.
               </code></pre>
        </section>

        <section>
          <h2>Typ Kompatibilität</h2>
          <em
            >Im Gegensatz zu Java/C# ("nominal typing") sind bei TypeScript zwei Typen kompatibel, sofern sie
            <b>dieselbe Struktur</b> haben ("structural typing")</em
          >
          <pre><code data-trim contenteditable class="line-numbers typescript" data-leftpad>
interface Book {
	title: string
}

interface Movie {
	title: string
}

const book:Book = { title: "Das Kapital" };
const movie:Movie = book; // OK, obwohl Book !== Movie
               </code></pre>
        </section>
        <section>
          <h2>Generics</h2>
          <p>Generische Typen verwenden</p>
          <pre><code data-trim contenteditable class="line-numbers typescript" data-leftpad>
interface Person { name: string };
interface Movie { title: string };

let persons:Array&lt;Person&gt; = [];
let movies:Array&lt;Movie&gt; = [];

persons.push({name: 'Klaus'});
movies.push({title: 'Batman'});

persons.push({title: 'Casablanca'}) // error ('title' not in Person)

persons = movies; // error

      </code></pre>
        </section>
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