Package Exports

ast-types
ast-types/def/core
ast-types/def/e4x
ast-types/def/es6
ast-types/def/mozilla
ast-types/lib/shared
ast-types/lib/traverse
ast-types/lib/types

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (ast-types) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

AST Types

This module provides an efficient, modular, Esprima-compatible implementation of the abstract syntax tree type hierarchy pioneered by the Mozilla Parser API.

Installation

From NPM:

npm install ast-types

From GitHub:

cd path/to/node_modules
git clone git://github.com/benjamn/ast-types.git
cd ast-types
npm install .

Basic Usage

var assert = require("assert");
var n = require("ast-types").namedTypes;
var b = require("ast-types").builders;

var fooId = b.identifier("foo");
var ifFoo = b.ifStatement(fooId, b.blockStatement([
    b.expressionStatement(b.callExpression(fooId, []))
]));

assert.ok(n.IfStatement.check(ifFoo));
assert.ok(n.Statement.check(ifFoo));
assert.ok(n.Node.check(ifFoo));

assert.ok(n.BlockStatement.check(ifFoo.consequent));
assert.strictEqual(
    ifFoo.consequent.body[0].expression.arguments.length,
    0);

assert.strictEqual(ifFoo.test, fooId);
assert.ok(n.Expression.check(ifFoo.test));
assert.ok(n.Identifier.check(ifFoo.test));
assert.ok(!n.Statement.check(ifFoo.test));

Custom AST Node Types

The ast-types module was designed to be extended. To that end, it provides a readable, declarative syntax for specifying new AST node types, based primarily upon the require("ast-types").Type.def function:

var types = require("ast-types");
var def = types.Type.def;
var string = types.builtInTypes.string;
var b = types.builders;

// Suppose you need a named File type to wrap your Programs.
def("File")
    .bases("Node")
    .build("name", "program")
    .field("name", string)
    .field("program", def("Program"));

// Prevent further modifications to the File type (and any other
// types newly introduced by def(...)).
types.finalize();

// The b.file builder function is now available. It expects two
// arguments, as named by .build("name", "program") above.
var main = b.file("main.js", b.program([
    // Pointless program contents included for extra color.
    b.functionDeclaration(b.identifier("succ"), [
        b.identifier("x")
    ], b.blockStatement([
        b.returnStatement(
            b.binaryExpression(
                "+", b.identifier("x"), b.literal(1)
            )
        )
    ]))
]));

assert.strictEqual(main.name, "main.js");
assert.strictEqual(main.program.body[0].params[0].name, "x");
// etc.

// If you pass the wrong type of arguments, or fail to pass enough
// arguments, an AssertionError will be thrown.

b.file(b.blockStatement([]));
// ==> AssertionError: {"body":[],"type":"BlockStatement","loc":null} does not match type string

b.file("lib/types.js", b.thisExpression());
// ==> AssertionError: {"type":"ThisExpression","loc":null} does not match type Program

The def syntax is used to define all the default AST node types found in https://github.com/benjamn/ast-types/blob/master/lib/core.js, https://github.com/benjamn/ast-types/blob/master/lib/es6.js, https://github.com/benjamn/ast-types/blob/master/lib/mozilla.js, https://github.com/benjamn/ast-types/blob/master/lib/e4x.js, and https://github.com/benjamn/ast-types/blob/master/lib/xjs.js, so you have no shortage of examples to learn from.