missing 'Access-Control-Allow-Origin'

[Bangee]

I’ll try to grab some informations from a JSON Data feed.
But I’ve got always this error:

Quellübergreifende (Cross-Origin) Anfrage blockiert: Die Gleiche-Quelle-Regel verbietet das Lesen der externen Ressource auf http://beny.ch/ironman/2015. (Grund: CORS-Kopfzeile 'Access-Control-Allow-Origin' fehlt).
ironman: Could not load data.

console.error(message);

Datalink:
http://beny.ch/ironman/2015

here is the code to grab the content:

		var ironmanRequest = new XMLHttpRequest();
		ironmanRequest.open("GET", url, true);
		ironmanRequest.onreadystatechange = function() {
			if (this.readyState === 4) {
				if (this.status === 200) {
					self.processIronman(JSON.parse(this.response));
				} else if (this.status === 401) {

					self.updateDom(self.config.animationSpeed);

					Log.error(self.name + ": Error forbidden");
					retry = false;
				} else {
					Log.error(self.name + ": Could not load data.");
				}

				if (retry) {
					self.scheduleUpdate((self.loaded) ? -1 : self.config.retryDelay);
				}
			}
		};                
		ironmanRequest.send();

How can I fix that?

Thanks for helping me

[KirAsh4]

This comes up quite often, not just here on the MM² forums, but out in the wild too:

http://lmgtfy.com/?q=Access-Control-Allow-Origin

Basically the answer is: you can’t do that … cross-domain … security … find proper API … all of the above …

[RedNax]

@KirAsh4 Well, not strictly true https://forum.magicmirror.builders/topic/157/mmm-opentherm
But yes, you’ll need to fix the source!

[paviro]

Just use a node_helper.js to get around the access-allow-origin policy.

[Bangee]

After googleing 1000 different websites I’ve used the nood_helper.js solution.

And to load the nood_helper.js I had to restart electron. pm2 restart mm
that coast me another hour to find out why it was no loading

[KrawallKurt]

I am facing the same problem. Could you please give an example, how you used node_helper.js to circumvent the access-allow-origin policy?

Thanks!

[yawns]

Like here for example:
https://github.com/yawnsde/MMM-RNV

You use request instead.

[KrawallKurt]

Thank you!

And why does it have to be in node_helper, not in the main script? Sorry, if this question sounds stupid, I’m new to developing modules.

Also, is there a reason for declaring var self = this; and using self.func instead of this.func? I have seen this quite a bit and couldn’t understand why people do this…

[yawns]

@KrawallKurt
Please note I am not an experienced javascript developer either. When using addon modules/libraries like request you use the node_helper.js to load this library. I am not sure if it is not possible at all to do so in the main module file or if it is just complicated. Maybe @strawberry-3-141 can clarify

self = this was used in other modules and I added it to my module as well, because I did not want to possibly break something by leaving it out. There is a lot of discussion on the web why this is used and if this still should be used.

[KrawallKurt]

Concerning the self=this question, I found a neat article giving som explanations: https://alistapart.com/article/getoutbindingsituations

The other question: Could it be, that node_helper is executed on the server and the main script is executed on the client?