Ast-query NPM | npm.io

AST Query

This project is a tentative to create a simple JavaScript AST modification library.

If you've ever worked with AST trying to edit source code, you'll know it is a bad time. AST syntax is terse and forces you to loop a tree and use conditional structure a lot. AST Query hide these complexities behind a declarative façade.

Making the simplicity choice means AST Query won't try to cover the full AST API. Rather we strive to answer commons needs.

Getting Started

Install: npm install --save ast-query

First, you need to pass a program code into AST query:

var program = require("ast-query");
var tree = program("var a = 'foo'");

This function returns a wrapped AST tree you can query and modify.

Once you've modified the AST, get the source code back by calling the toString method on the tree.

// ...
tree.var("a").value("'bar'");

console.log( tree.toString() );
// LOG: var a = 'bar';

Remember that you are editing source code. This mean you provide raw source code strings. This mean you need to double wrap strings (e.g.: "'foo'"). If that's not done, AST-query assume you're referencing a variable called foo.

API

Program

`var tree = program( sourceCode, escodegenOptions, esprimaOptions )`

sourceCode (String) - The source code to edit.
escodegenOptions (Object) optional - escodegen option object
acornOptions (Object) optional - acorn option object

Returns an AST tree you can then query as explained below:

`tree.var( name )`

name (String) - The variable name

Find and returns a Variable node.

Given this code

var bar = 23;

You'd call tree.var('bar') to get the Variable node.

`tree.callExpression( name )`

name (String) - The name of the function or method being called.

Find a function or method call and return a CallExpression node

Given this code

grunt.initConfig({});

You'd call tree.callExpression('grunt.initConfig') to get the CallExpression node.

`tree.assignment( assignedTo )`

assignedTo (String) - The name (name or object) a value is assigned to

Find and return an AssignmentExpression node.

You'd call tree.assignment('module.exports') to query the code below:

module.exports = function () {
  // code
};

`tree.body`

Property representing the program body in a Body node.

`tree.verbatim( body )`

body (String) - The source code to inline verbatim

Adds body and return a token assigment.

tree.body.append('var a = 1;' + tree.verbatim('ANYTHING'));

Variable node

`.value( value )`

value (String) optionnal - A string containing the new variable value.

It returns the current or new value wrapped in AST query interface.

`.rename( name )`

name (String) - Change the variable name

CallExpression node

`.filter( iterator )`

iterator (Function) - Function receiving each node as arguments and returning true to keep the current node in the returned set.

Return a new CallExpression nodes collection with nodes passing the iterator test.

`.arguments`

A property pointing to an ArrayExpression node referencing the called function arguments.

AssignmentExpression node

`.value( value )`

Replace the assignment value with a new value or return the current value wrapped in an AST query interface.

Literal node

A Literal node represent a raw JavaScript value as a String, a Number or a Boolean.

`.value( value )`

Get or update the value.

FunctionExpression node

Node representing a function declaration (e.g. function () {}).

`.body`

Property pointing to a Body node representing the function expression body.

ObjectExpression node

`.key( name )`

name (String) - Key name Get a key value object or create a blank placeholder

`value( value )`

Replace current node with a new value. Returns the new value wrapped.

ArrayExpression node

`.push( value )`

value (String) - value to push in the array

`.unshift( value )`

value (String) - value to unshift in the array

`.at( index )`

index (Number) - Index of the value to fetch

Returns a value wrapped in an AST query interface.

`value( value )`

Replace current node with a new value. Returns the new value wrapped.

Body node

`.prepend( code )`

Preprend the given code lines in the body. If a "use strict"; statement is present, it always stay first.

`.append( code )`

Append the given code lines in the body.

Contributing

Style Guide: Please base yourself on Idiomatic.js style guide with two space indent Unit test: Unit test are wrote in Mocha. Please add a unit test for every new feature or bug fix. npm test to run the test suite. Documentation: Add documentation for every API change. Feel free to send corrections or better docs! Pull Requests: Send fixes PR on the master branch. Any new features should be send on the wipbranch.