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Prorammierung in JS

JSON mit JavaScript Verwendung

  • Daten transferieren
  • user Input
  • Daten speichern
  • Daten validieren

Same-origin policy

verbietet andere Quellen

CORS

  • Cross-Origin Resource Sharing.
  • ermöglicht vertrauenswürdige Origins
  • HTTP-Header: Access-Control-Allow-Origin

JSONP

  • JSON with Padding
  • Daten laden via embedded resources
  • umgehen der same-origin policy
  • JS kommt zurück, ruft callback auf
  • (-) Kein Errorhandling
  • (-) JSONP unsicher wegen einfachem cross-side scriptinjection

JSON in JavaScript

var movie = { number: 1, title: "Dr. No" };
var movieStr = JSON.stringify(movie);
var movieAgain = JSON.parse(movieStr);

Asynchroner AJAX-Call

var request = new XMLHttpRequest();
request.onreadystatechange = function() {
  if (this.readyState === 4 && this.status === 200) {
    var catalog = JSON.parse(this.responseText);
    console.log(catalog.movies[0].title);
  }
};
request.open('GET', 'https://ma.ch', true);
request.send()

Synchroner AJAX-Call

const catalog = JSON.parse(request.responseText);
const now = new Date().toLocaleTimeString();
catalog.movies[0].title = "Modified at " + now;

// convert to string and upload to server
const data = JSON.stringify(catalog.movies[0]);
request.open("PUT", "https://ma.ch/0", false);
request.send(data);