Avoiding JavaScript PitfallsThrough Tree Hugging

Zef Hemel (@zef)

JavaScript Developer

http://c9.io

we’re building#1 JavaScript IDE

~400,000

Iterating using undeclared variable

Warning: you are in an anonymous inner function with its own “this” pointer -- ya sure this is what you mean?

Did you mean “length”?

How?

Unleash the awesome power of...

tatic

taticX

program analysis

Whatcan you do with it?

code outlines

code navigation

...

code completion (intellisense)

Parse

Analyze

ParserCode AST

Abstract Syntax Tree

a * 10 Parser

Op

Var Num“*”

“a” “10”

Zeon

UglifyJS

Narcissus

Esprimalanguage.js

performance (speed/memory)

AST datastructure

traversal tools

performance (speed/memory)

AST datastructure

traversal tools

JavaSc

ript s

pecific

treehugger.js

“The JQuery of AST analysis.”

Standard AST Datastructure

Standard Traversals

Pattern Matching

+

a * 10

Op

Var Num“*”

“a” “10”

Op("*", Var("a"), Num("10"))

Op

Var Num“*”

“a” “10”

Op("*", Var("a"), Num("10"))

ATerm

Op

Var Num“*”

“a” “10”

Constructors

Lists

Strings

Var(_)

[_, _]

"hello"

Placeholders x

http://github.com/ajaxorg/treehugger

http://c9.io @zef @cloud9ide

http://github.com/ajaxorg/treehugger