As presented at @media Ajax in London on the 20th November 2007.

1. Metaprogramming
JavaScript
Dan Webb (dan@danwebb.net)

2. What?
“ the writing of computer programs
that write or manipulate other
programs (or themselves) as their
data”

3. With JavaScript?!
★ Small and fiesty but widely misunderstood
★ Relies on few but powerful constructs
★ You can work with functions, arguments,
built-ins types and mechanisms like
inheritance at runtime
★ Techniques underpin many JS libraries

4. JavaScript Exposed:
Objects Out Of
Control!

5. Play along!

6. 4 building blocks

7. (Nearly) everything
is a hash

8. number
string
boolean
undefined

9. everything else is an
Object

11. This works with
any object

13. Expandos: a special case

17. Inspecting objects

20. Inspecting types

24. Wha?!

26. First typeof
then instanceof

27. Functions are Objects

29. 'Methods' are just
functions that are
assigned to a property
of an object

38. arguments

42. Functions can return
other functions

45. Closure

46. Back to wikipedia...
“
A closure occurs when a function
is defined within another function,
and the inner function refers to
local variables of the outer
function.

49. Why is that useful?

53. Functions can be used
to make objects

55. Constructor functions
are just functions

56. The magic is in
the new operator

60. inheritance

67. The point is:
its all just functions,
objects and properties

68. We can hack it all.

69. So what can you do
with this stuff?

70. Patch holes in
bad implementations

73. Self optimising code

76. Pretty APIs

79. Domain Specific
Languages

80. DOMBuilder
http://danwebb.net/lowpro

84. DIY language features

85. John Resig's method
overloading
http://ejohn.org/blog/javascript-method-overloading/

89. Prototype 1.6 Classes
http://prototypejs.org/learn/class-inheritance

92. and a lot more...

93. Looking back...
★ JavaScript is small but totally flexible
★ A handful of techniques provide everything
you need
★ It's all about objects, properties and
functions
★ Don't worry if its not all sunk in. Have a
play around. Slides will be available.

94. Coming Soon...