Is it possible to open native iOS app, e.g. calendar or notes, from an HTML link which is in website? I tried to find an example but I couldn't. I ran into these URL schemes but I don't know how to use them and what's the URL scheme for calendar or notes. Is it possible just to do something like this:
<a href="calendar://something here?">Click me!</a>
Is it possible to do it only with HTML or is JavaScript needed?
Yes you can very well possible to do that. You're right in placing the link like this:
<a href="calendar://">Click me!</a>
Now go to your iOS app's info.plist file. In that add the following tags:
<key>CFBundleURLTypes</key>
<array>
<dict>
<key>CFBundleURLName</key>
<string>com.companyname.appname</string>
<key>CFBundleURLSchemes</key>
<array>
<string>calendar</string>
</array>
</dict>
</array>
Save the plist file and exit it. After this when you open the web page in Safari browser of your iOS device and click on the link, your iOS app will invoke. I hope it helps!