4 ms·

I used to really feel the same, and tried to make no-js sites for a bit. Long story short, eventually you're going to want some user interaction beyond submitt

I used to really feel the same, and tried to make no-js sites for a bit. Long story short, eventually you're going to want some user interaction beyond submitting forms, and if you've built your site as anything other than a js SPA, it's quickly going to become ugly.

kiwidrew 6y ago
I wonder, would it be possible to identify a subset of Javascript that is benign? Perhaps some rules about which functions the script is permitted to use, along with restrictions on looping constructs (iterate through an array = OK; unbounded recursion = not OK)... That way simple stuff like: var form = document.forms[0]; document.getElementById('foo').addEventListener('change', function (e) { if (e.target.value == 'xyzzy') form.elements['bar'].classList.add('show'); } ); would be perfectly fine, but crazy "let's exploit the JIT" or "emulate an entire 8-bit home computer" stuff would be rejected. And then, as a bonus, we could dump the entire JIT infrastructure and go back to a simple JS interpreter (a la Duktape) because there just wouldn't be much code left to interpret in the first place.
- bigiain 6y ago
  > (iterate through an array = OK; unbounded recursion = not OK)... Right, so all we need to do is solve the halting problem... <smirk>
  - userbinator 6y ago
    The halting problem is about the general case, but when deciding a sane subset of JS, one can always be more conservative.
    - saagarjha 6y ago
      Yeah, if your subset of JavaScript is not Turing complete.
  - kiwidrew 6y ago
    Yeah, so some syntactic rules (using Array.forEach() instead of for(;;) loops) and prohibiting some of Javascript's more dynamic features might be enough to render the language non-Turing complete. It would also -- and this is kind of the point -- render the language unable to perform certain computations that plain vanilla Javascript can perform.
- anonms-coward 6y ago
  If you can prove whether recursion or even a loop is bounded or not, you have solved the collatz conjecture.

kiwidrew 6y ago

I wonder, would it be possible to identify a subset of Javascript that is benign? Perhaps some rules about which functions the script is permitted to use, along with restrictions on looping constructs (iterate through an array = OK; unbounded recursion = not OK)... That way simple stuff like: var form = document.forms[0]; document.getElementById('foo').addEventListener('change', function (e) { if (e.target.value == 'xyzzy') form.elements['bar'].classList.add('show'); } ); would be perfectly fine, but crazy "let's exploit the JIT" or "emulate an entire 8-bit home computer" stuff would be rejected. And then, as a bonus, we could dump the entire JIT infrastructure and go back to a simple JS interpreter (a la Duktape) because there just wouldn't be much code left to interpret in the first place.

bigiain 6y ago
> (iterate through an array = OK; unbounded recursion = not OK)... Right, so all we need to do is solve the halting problem... <smirk>
- userbinator 6y ago
  The halting problem is about the general case, but when deciding a sane subset of JS, one can always be more conservative.
  - saagarjha 6y ago
    Yeah, if your subset of JavaScript is not Turing complete.
- kiwidrew 6y ago
  Yeah, so some syntactic rules (using Array.forEach() instead of for(;;) loops) and prohibiting some of Javascript's more dynamic features might be enough to render the language non-Turing complete. It would also -- and this is kind of the point -- render the language unable to perform certain computations that plain vanilla Javascript can perform.
anonms-coward 6y ago
If you can prove whether recursion or even a loop is bounded or not, you have solved the collatz conjecture.