On the Mac, you can enable continuous spell checking by calling -[NSTextField setContinuousSpellCheckingEnabled:YES]. On iOS, continuous spell checking is on by default.
If you want to put together really simple interactions, then a web page will get you off the ground fast. The problem is when you get to the details. Harder things become more difficult, or just impossible.
For example, I don't think there's any way to control a browser's spell checker, beyond turning it on and off for a given field. (Correct me if I'm wrong.)
In a native app, I have implemented functionality so the spell checker would ignore text with a certain pattern, but spell check the rest of the input.
If you want to put together really simple interactions, then a web page will get you off the ground fast. The problem is when you get to the details. Harder things become more difficult, or just impossible.
For example, I don't think there's any way to control a browser's spell checker, beyond turning it on and off for a given field. (Correct me if I'm wrong.)
In a native app, I have implemented functionality so the spell checker would ignore text with a certain pattern, but spell check the rest of the input.