Sergi shows an easy way to extend the syntax of JavaScript without having to create a new language. Using sweet.js macros created by Mozilla's Tim Disney, we can extend our favorite language without making big sacrifices, we can add a few small features to our favorite language or we can create entire DSLs that help with the problem at hand, all in an easy way.

1. Extending JavaScript
the easy way
Sergi Mansilla, November 2012

2. @sergimansilla

3. JavaScript is popular

4. It is ASM
for the web

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Source: http://altjs.org

6. Be JavaScript, my friend

7. ...but it is far
from perfect

9. Macros
ultimate flexibility
(ES6 won't have them, btw)

10. Macros provide a way
to extend syntax
Syntax Macro Syntax

11. Users can extend the
language

12. It helps evolving the
language faster

13. sweet.js
Macros for JavaScript

14. sweet.js
Modeled after
Scheme macros

15. Sweet.js
Syntax Macro Syntax
JS + Macros Sweet.js JS

16. Redefine 'function'

17. Redefine 'function'

18. Destructuring

19. Destructuring

20. Destructuring

21. Destructuring

22. Destructuring

23. Destructuring

24. Destructuring

25. ?

26. ?

27. Nice ranges!

28. case-style assignment

29. case-style assignment

30. Use cases
Try proposed syntax before it makes into the language
Create Micro-DSLs for your scenario
Use ideas from other languages
Make the new <your-silly-name-here>Script
Implement basic types
You get the idea

31. Start using it now
Node.js
> npm install sweet.js
> sjs -o output.js test_macros.sjs
> node output.js
Browser
https://github.com/iammerrick/require-sweet

32. Questions?

33. Thanks!
@sergimansilla
github.com/sergi
sergimansilla.com

34. References
http://sweetjs.org/
https://github.com/mozilla/sweet.js
http://jlongster.com/why-sweet.js-matters
http://scriptogr.am/micmath/post/sweet-macros-in-
javascripthttps://news.ycombinator.com/item?id=4560691
http://youtu.be/_ahvzDzKdB0