ast-walk provides an easy way to inspect the ast
created by javascript parsers. The interface provided is a lot like a typical shell,
with familiar commands like cd
and ls
.
From the command line, it will load javascript files from disk and use recast
to parse them. You can also provide ast's (potentially from other parsers) via code.
This project is a fork of jwalk which provides essentially the same
utility for large JSON objects.
Installation
More documentation (and fewer bugs) coming soon. In the meantime, install it via npm:
npm install -g ast-walk
Running
And then run it like this:
ast-walk somefile.js
It can also handle gzipped files. If the extension is .gz, it will decompress the javscript automatically.
(This is a left over feature from jwalk, and unlikely to be useful in the javascript context).
ast-walk somefile.js.gz
Most of the documentation below is unmodified from jwalk, and so discusses json. Just apply the same
principles to your ast nodes. New ast specific commands include print and find.
Possible Commands
Given the following json file
{
"name": "jwalk",
"version": "0.0.4",
"description": "command-line json inspector",
"preferGlobal": "true",
"repositories": {
"type": "git",
"url": "http://github.com/nkohari/jwalk"
},
"bin": {
"jwalk": "bin/jwalk"
},
"dependencies": {
"coffee-script": "1.4.0",
"colors": "0.6.0-1",
"filesize": "1.6.6",
"underscore": "1.4.2"
},
"engine": "node >= 0.8.x"
}
Help
Shows this help message
jwalk obj{8} / $ help
cd navigates through nodes in the tree
clear clears the screen
cls clears the screen
exit quit jwalk
find performs a depth first search for the given node type
help shows this help message
keys examines the keys of an object node
ls examines a single node
print prints the ast at this point
quit quit jwalk
Print
Prints the javascript at the current node
ast-walk obj{4} /program/body/0 $ print
function hello(name){
console.log('hello ' + name);
}
Find
Perform a depth first search for a given node type.
The first argument supplied is the desired node type to find and provides autocompletion hints
ast-walk obj{4} / $ print
var a = 'hello';
function helloMessage(name){
return 'hello ' + name;
}
function byeMessage(name){
return 'bye ' + name;
}
function hello(name){
console.log(message(name));
}
ast-walk obj{4} / $ find ReturnStatement
ast-walk obj{3} /program/body/1/body/body/0 $ print
return 'hello ' + name;
ast-walk obj{3} /program/body/1/body/body/0 $ cd /
ast-walk obj{4} / $ find FunctionDeclaration 1
ast-walk obj{3} /program/body/2/body/body/0 $ print
function byeMessage(name){
return 'bye ' + name;
}
The optional second argument allows you to skip the first X elements of a given type.
find FunctionDeclaration 2
would skip the first 2 FunctionDeclarations returning the third.
Note that when a node is "skipped", none of it's children will be searched, this allows
a (sorta-kinda) breadth first search. You can create a chain as long as you'd like:
ast-walk obj{4} / $ find FunctionDeclaration 2 IfStatement 2 IfStatement ReturnStatement
List
Examines the current node
ast-walk obj{8} / $ ls
{ name: 'jwalk',
version: '0.0.4',
description: 'command-line json inspector',
preferGlobal: 'true',
repositories:
{ type: 'git',
url: 'http://github.com/nkohari/jwalk' },
bin: { jwalk: 'bin/jwalk' },
dependencies:
{ 'coffee-script': '1.4.0',
colors: '0.6.0-1',
filesize: '1.6.6',
underscore: '1.4.2' },
engine: 'node >= 0.8.x' }
Change Directory
Allows navigation through the JSON tree. Note 'cd' does support autocomplete by pressing the tab key.
ast-walk obj{8} / $ cd dependencies
ast-walk obj{4} /dependencies $ ls
{ 'coffee-script': '1.4.0',
colors: '0.6.0-1',
filesize: '1.6.6',
underscore: '1.4.2' }
Clear
Clears the screen
ast-walk obj{8} / $ clear
or
ast-walk obj{8} / $ cls
Keys
Examines the keys of a node
ast-walk obj{8} / $ keys
[ 'name',
'version',
'description',
'preferGlobal',
'repositories',
'bin',
'dependencies',
'engine' ]
Quit
Exits the ast-walk application
ast-walk obj{8} / $ exit
or
ast-walk obj{8} / $ quit
Preferences File
You can create a JSON file at ~/.ast-walk
to define preferences. Right now, all it supports is defining aliases for commands, like so:
{
"aliases": {
"l": "ls"
}
}
Contributing
Bug reports and pull requests welcome!