Initially did not see anything thanks to Ghostery + RequestPolicy. Since all the JavaScript disablers tend to trigger the haterade dispensers, I also checked to see whether or not they had anything in place for the search bots:<p><a href="https://www.google.com/#q=site:helloblock.io+how+to+build+a+bitcoin+wallet" rel="nofollow">https://www.google.com/#q=site:helloblock.io+how+to+build+a+...</a><p><pre><code> > Your search - site:helloblock.io how to build a bitcoin wallet -
> did not match any documents.
</code></pre>
Too bad, as 'building a bitcoin wallet' is certainly worth ranking for (and the content is certainly high quality)!
This is fine for learning about Bitcoin, but don't use this is in production. No matter how secure you think you are, someone can likely get into your server and serve their own JavaScript (making your clients send all their money and/or keys). Also, this tutorial uses a Bitcoin centralized service to communicate with the network, and you have to trust that they won't feed you false information/withhold transactions/perform malleability attacks.
What kind of security concern would there be with using JS to implement your wallet? Or building the wallet yourself as opposed to a solution with updates and whatnot?
I thought several times about building a bitcoin wallet but I'm just too worried that I'll get something wrong and either lose a key or accidentally make a transaction that loses coins so decided not to risk it even for my own use. I'd frankly be terrified to let anyone else risk their own money on something like that without extreme levels of code review etc.
These kind of handson tutorials are awesome. You can just copy/paste and run the code inside the browser console and see your transaction propagate to the network. I wish more tutorials were as easily 'runnable'.