A summary of Douglas Crockford's amazing book "JavaScript: The Good Parts". First presented at the Baltimore/DC JavaScript Users Group on 7/7/2009. http://www.meetup.com/baltimore-dc-javascript-users/calendar/10560330/

1. JavaScript: The Good Parts
@jonathanjulian

4. crockford.com

5. First, the Bad Parts

6. globals. optional ;
truthy/falsy. scope.

7. Then, the Good Parts!

8. functions as objects. loose typing.
dynamic objects. literals.

9. The Bad Parts

10. globals
• x = 1;
• var y = 1;
• x is in the global namespace
• YourAppName.x = 1;

11. line termination
• semi-colons are INSERTED by the parser
• optional semi-colons are not a “language
feature”
• you are not warned

12. truthy / falsy

13. ==

14. ===
All of these are false

15. take advantage
• if (x)
• if (myobject.propery)
• if (myobject.property == null) // no, No, NO!
• test for exactly what you want to test for
• ...or not
• KNOW THE FALSY VALUES
undefined, null, false, 0, ‘’, NaN

16. no block scope
• functions create scope
• blocks do not

17. The Good Parts!

18. functions are objects
• can be passed, returned
• have scope
• have closure

19. loose typing
• no compiler
• no type heirarchies

20. objects are dynamic
• members can be added to any object, any time
• helpful to attach attributes

21. object literals
• aka JSON
• { count: 2, prefix: ‘pre_’ }
• pass options to functions
• JSON as communication
• JSON as persistence
• etc

22. Know the bad parts are
there...and avoid them

23. Learn and love the
good parts!

24. tools
• FireBug
• JSLint
• spidermonkey / rhino / v8

25. takeaway
• think about vars and scope
• never use ==
• if (myobject) {
• jslint.com

26. JavaScript is a beautiful
language

27. jonathan.m.julian@gmail.com
@jonathanjulian
jonathanjulian.com