Thursday, 13 August, 2015 UTC
Summary
Did you know you could use C preprocessor even for JavaScript files? (yes, it doesn't care about syntax that much)
Say, we want to implement C-like "modules" (inclusions) in JavaScript.
Create first file
1.js (filenames don't matter) like this: #ifndef HELLO_1
#define HELLO_1
console.log('hello');
#endif
(
#ifndef/#define is standard C practice for avoiding double-inclusion)Then, create
2.js: #ifndef HELLO_2
#define HELLO_2
#include "1.js"
console.log('world');
#endif
And now you can bundle them into one file with:
cpp -P -Wundef -nostdinc -Wtrigraphs -C 2.js
(here we ask
cpp just to preprocess our file with basic warning and preserving comments; also we ask not to search standard C library for includes)And as a result you would get:
console.log('hello');
console.log('world');
Note that you can even define and use full-featured macroses inside of your JavaScript - just
#define them and ready to go!P.S. Yes this is a crazy hack (as most of other stuff in my blog), and there are more appropriate tools for transforming JavaScript, but why not to try if we can? :)
UPD [17.08.2015]: Turns out it's not as crazy experiment as I initially thought. Ryan Grove on Twitter just mentioned that they actually used this technique at Yahoo Search in 2007:
@RReverser Believe it or not, we used this technique in our production JS workflow at Y! Search ~2007. Worked well. http://t.co/HGSFfU1W1u— Ryan Grove (@yaypie) August 16, 2015