Error handling in JavaScript

Handle with careFehlerbehandlung in JavaScript

Friday 8 November 13

WER BIN ICH?

• Sebastian Springer

• https://github.com/sspringer82

• @basti_springer


https://github.com/sspringer82


Was ist ein Fehler?

☠Friday 8 November 13

Was ist ein Fehler?

☠Whoops, this should not happen.


Fehlertypen


Eigene Fehler

throw new Error('An error occurred');


Eigene Fehler

var MyErr = function (message) { this.message = message; this.name = 'MyErr';}

MyErr.prototype = new Error();MyErr.prototype.constructor = MyErr;


Abfangen von Fehlern

try { throw new Error('Hello World');} catch (e) { console.log(e);} finally { console.log('Finished');}



try {

} catch (RangeError e) { }



try {

} catch (e) { if (e instanceof RangeError) { }}


Callbacks


Fehler in CallbacksApplikation Asynchrone

Ausführung



Ausführung

Operation



Ausführung

Operation

☠☂ ☏☣☢



Ausführung

Operation

Callback☠☂ ☏☣☢


Fehler in Callbacksfunction myTimeout() { throw new Error("whoops");}



try { setTimeout("myTimeout()", 0);} catch (e) { console.log(e);}



try { setTimeout("myTimeout()", 0);} catch (e) { console.log(e);}

☠Friday 8 November 13

Fehler in Callbacks$.ajax({ url: ‘/something’, success: function (data) { ... }, error: function (data) { ... }});


Fehler in Callbacks

var fs = require('fs');

fs.readFile('file', function (err, d) { ...});


Fehler in Callbacks

var fs = require('fs');

fs.readFile('file', function (err, d) { ...});

null


Fehler in Callbacks

Error { errno: ... code: ... path: ... message: ...}


Events


Error EventsSubject Observer


Error Events

on(‘error’, function...

Subject Observer


Error Events

☠☂ ☏☣☢


Subject Observer


Error Events

☠☂ ☏☣☢


trigger(‘error’, {...

Subject Observer


Promiseshttp://wiki.commonjs.org/wiki/Promises


http://wiki.commonjs.org/wiki/Promises

http://wiki.commonjs.org/wiki/Promises

Promises

In Javascript, promises are objects which represent the pending result of an asynchronous operation.

(Martin Fowler)


Promises$.ajax({ url: ‘/my/url’}).done(function (data) { ...}).fail(function (data) { ...}).always(function (data) { ...});


Promisesfunction promisedFunc() { var def = $.Deferred(); // do something asynchronous // success def.resolve(); // fail def.reject(); return def.promise();}


Promises

promisedFunc().done(function () { // success}).fail(function () { // failure}).always(function () { // success & failure});


Promises

$.when( promisedFunc(), promisedFunc()).then(success, failure);


Promises

• http://api.jquery.com/category/deferred-object/Client only

• https://github.com/kriskowal/qClient + Server

• https://github.com/kriszyp/node-promiseServer only


http://api.jquery.com/category/deferred-object/

http://api.jquery.com/category/deferred-object/

https://github.com/kriskowal/q

https://github.com/kriskowal/q

https://github.com/kriszyp/node-promise

https://github.com/kriszyp/node-promise

Node.js Domain


Node domain

var domain = require(‘domain’).create();domain.on(‘error’, function (err) { console.log(err);});

domain.run(function () { ...});


Node Domain

• error-Events

• Exceptions

Wird ausgeführt bei:


window.onerror


window.onerror

catch it all!


window.onerror

window.onerror = function (msg, url, nr){ ... return true;}


window.onerror

window.onerror

Code


und jetzt?


und jetzt?

Logging FTW!


Logging

Client Server


Logging

Client

☠☂ ☏☣☢

Server


Logging

Client

☠☂ ☏☣☢

ServerLog Message


Loggingwindow.onerror = function (msg, url, nr){ $.ajax({ url: ‘/logger’ data: { msg: msg, url: url, nr: nr } }); return true;}Friday 8 November 13

Logging

Fire and Forget


Fragen?


Sebastian [email protected]

Mayflower GmbHMannhardtstr. 680538 MünchenDeutschland

@basti_springer



mailto:[email protected]

mailto:[email protected]



Error handling in JavaScript

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