small preprocessor - #ifdef like statement ?

Hi Gordon,

It would be very nice if a tiny preprocessor with #ifdef / #endif statements where included in WebIDE. I would like to strip out debug code that way.

Regards

Sacha

Hmm, it's a thought. I wonder whether minification could be modified to do what you want though. For instance:

var DBG = false;

if (DBG) console.log("Debug");
console.log("Foo");

That actually works fine when minified - it goes down to:

var DBG=!1;console.log("Foo");

However when in a function, it doesn't work properly (because it thinks that the state of DBG might get changed). Object.freeze doesn't seem to work either. You could do:

(function() {
  var DBG = false;

  function foo() {
    if (DBG) console.log("Debug");
    console.log("Foo");
  }

  setTimeout(foo,1000);
})();

And that minifies down really nicely:

(function(){setTimeout(function(){console.log("Foo")},1E3)})();

Hello Gordon,

Adding such a feature to the minifcation would be great.

Regards

Sacha

There are several new syntax proposals for ES7 that would like to make use of "#", as it's one of the last ascii characters available. I strongly recommend avoiding the introduction of non-standard syntactic forms.

@rwaldron: any thoughts on telling the minifier that DBG is a constant that doesn't change? It sounded like DBG=Object.freeze(DBG) might do it, but it didn't seem to work in the closure compiler.

Right, that won't work—Object.freeze only sets the meta object descriptor properties to: [[configurable]]: false, [[writable]]: false. It won't turn a non-object into a const. What you could do is provide a "built-in" keyword whose value is true and is essentially a const binding. Special keywords are safe additions, as long as they're not any of the FutureReservedWords: class, enum, extends, super, const, export, import, implements, let, private, public, interface, package, protected, static or yield; additionally, there is precedent in node with bindings like process, which aren't const, but are special (if you attempt to reassign it, the process itself will crash)

I'm not talking about extending Espruino at all here... I can want a way to tell someone else's minifier that a value isn't going to change.

I guess I could pre-parse the code, detect the pattern var DBG = true/false; at the beginning, and then search/replace DBG with the actual value before passing the code to the minifier. It's pretty ugly though.

I see, I misunderstood.