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1.1.1 • Public • Published

ast-matcher Build Status

Create pattern based AST matcher function. So you don't need to be an AST master in order to do static code analysis for JavaScript.

npm install ast-matcher

This tool can be used in Node.js or browser. You may need some polyfill for missing JavaScript features in very old browsers.

First, choose a parser

Beware ast-matcher doesn't install a parser for you. You need to manually install one.

We support any parser compatible with ESTree spec. Here are some popular ones:

Take esprima for example, you need to use setParser to hook it up for ast-matcher.

const esprima = require('esprima');
const astMatcher = require('ast-matcher');
// with es6, import astMatcher, { depFinder } from 'ast-matcher';
// or pass options to esprima
astMatcher.setParser(function(contents) {
  return esprima.parse(contents, {jsx: true});

Beware @babel/parser needs estree plugin

const parser = require('@babel/parser');
const astMatcher = require('ast-matcher');
astMatcher.setParser(function(contents) {
  return parser.parse(contents, {
    // ... other options
    plugins: [
      // ... other plugins

For TypeScript user, use:

import * as astMatcher from 'ast-matcher';`
let { depFinder } = astMatcher;

API doc for two main functions: astMatcher and depFinder.


Pattern matching using AST on JavaScript source code.

const matcher = astMatcher('__any.method(__str_foo, [__arr_opts])')
matcher('au.method("a", ["b", "c"]); jq.method("d", ["e"])');
// => [
//      {match: {foo: "a", opts: ["b", "c"]}, node: <CallExpression node> }
//      {match: {foo: "d", opts: ["e"]}, node: <CallExpression node> }
//    ]

astMatcher takes a pattern to be matched. The pattern can only be single statement, not multiple statements. Generates a function that:

  • takes source code string (or estree syntax tree) as input,
  • produces matched result or undefined.

Support following match terms in pattern:

  • __any matches any single node, but no extract
  • __anl matches array of nodes, but no extract
  • __str matches string literal, but no extract
  • __arr matches array of partial string literals, but no extract
  • __any_aName matches single node, return {aName: node}
  • __anl_aName matches array of nodes, return {aName: array_of_nodes}
  • __str_aName matches string literal, return {aName: value}
  • __arr_aName matches array, extract string literals, return {aName: [values]}

__arr, and __arr_aName can match partial string array. [foo, "foo", "bar", lorem] => ["foo", "bar"]

use method(__anl) or method(__arr_a) to match method(a, "b");

use method([__anl]) or method([__arr_a]) to match method([a, "b"]);


Dependency analysis for dummies, this is a high level api to simplify the usage of astMatcher.

const depFinder = astMatcher.depFinder;
const finder = depFinder('a(__dep)', '__any.globalResources([__deps])');
finder('a("a"); a("b"); config.globalResources(["./c", "./d"])');
// => ['a', 'b', './c', './d']

depFinder takes multiple patterns to match, instead of using __str_/__arr, use __dep and __deps to match string and partial string array. Generates a function that:

  • takes source code string (or estree syntax tree) as input,
  • produces an array of string matched, or empty array.


1. find AMD dependencies

Beware AMD module could be wrapped commonjs module, you need to remove ['require', 'exports', 'module'] from the result.

const amdFind = depFinder(
  'define([__deps], __any)', // anonymous module
  'define(__str, [__deps], __any)' // named module
const deps = amdFind(amdJsFileContent_or_parsed_ast_tree);

2. find CommonJS dependencies

const cjsFind = depFinder('require(__dep)');
const deps = cjsFind(cjsJsFileContent_or_parsed_ast_tree);

3. match if statement

const matcher = astMatcher('if ( __any_condition ) { __anl_body }');
const m = matcher(code_or_parsed_ast_tree);
// => [
//   {
//     match: { condition: a_node, body: array_of_nodes },
//     node: if_statement_node
//   },
//   ...
// ]

4. match if-else statement

const matcher = astMatcher('if ( __any_condition ) { __anl_ifBody } else { __anl_elseBody }');
const m = matcher(code_or_parsed_ast_tree);
// => [
//   {
//     match: { condition: a_node, ifBody: array_of_nodes, elseBody: array_of_nodes },
//     node: if_else_statement_node
//   },
//   ...
// ]

5. find Aurelia framework's PLATFORM.moduleName() dependencies

const auJsDepFinder = depFinder(
  'PLATFORM.moduleName(__dep, __any)',
  '__any.PLATFORM.moduleName(__dep, __any)'
const deps = auJsDepFinder(auCode_or_parsed_ast_tree);

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