rubyqin/parsejs

ParseJS

ParseJS is a JavaScript parser written in Ruby using the KPeg parser generator. It also takes a JavaScript parse tree and emits semantically identical JavaScript. The parser is tested by parsing large, popular JavaScript libraries (such as jQuery) and confirming that the minified output after a round-trip through ParseJS is the same as minifying the original source.

The ParseJS stringifier does not guarantee equivalent whitespace and comments in a round-trip, but it should guarantee semantic equivalence.

The ParseJS parser maintains comments in most cases where comments would represent inline documentation.

• top-level statement: a ParseJS top-level statement node contains any comment that immediately preceded it.
• property: in a property list (object literal), a property node contains any comment that immediately preceded it.

There is a work-in-progress AST walker that associates comments with particular structures. The ultimate goal of this walker is to identify JavaScript structures that represent "classes" or similar structures and associate their comments with information extracted from the code.

Usage

ParseJS is provided as a Rubygem. At the moment, you can use it in your Gemfile by using Bundler's git feature.

gem "parsejs", :git => "git://github.com/wycats/parsejs.git"

You can parse a String of JavaScript and receive an AST by using ParseJS.parse.

ast = ParseJS.parse(some_data)

You can convert the AST back into a JavaScript String using the stringifier. You can mutate the AST before converting it into a String if you wish.

ParseJS::Stringifier.to_string(ast)

You can write your own AST walker without implementing visitors for all nodes by subclassing ParseJS::Visitor. Take a look at that class to see the default visitor behavior for a particular node.

By default, nodes accept their children. Nodes that have children that are Arrays of nodes (e.g. FunctionDeclaration, which has an Array of parameters and an Array of statements as children) default to looping over the Arrays and accepting their members.

You can take a look at the in-progress docs extractor or the stringifier for examples of subclasses of ParseJS::Visitor.

LICENSE

Copyright (C) 2012 Yehuda Katz

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.