esprima

What is esprima?

Esprima is a high performance, standard-compliant ECMAScript parser written in ECMAScript (also popularly known as JavaScript). It is capable of parsing JavaScript code to produce an abstract syntax tree (AST), which can be used for various purposes such as static analysis, code instrumentation, and transformation.

What are esprima's main functionalities?

Parsing JavaScript Code

This feature allows you to parse a string of JavaScript code and obtain an abstract syntax tree (AST) that represents the structure of the code.

const esprima = require('esprima');
const program = 'const answer = 42;';
const ast = esprima.parseScript(program);

Syntax Tree Analysis

Once you have the AST, you can analyze it to extract information about the code, such as variable names, function declarations, and more.

const esprima = require('esprima');
const program = 'const answer = 42;';
const ast = esprima.parseScript(program);
console.log(ast.body[0].declarations[0].id.name); // 'answer'

Tokenization

Esprima can also be used to tokenize JavaScript code, breaking it down into its lexical components (tokens) such as keywords, identifiers, literals, and operators.

const esprima = require('esprima');
const program = 'const answer = 42;';
const tokens = esprima.tokenize(program);
console.log(tokens);

Other packages similar to esprima

acorn

Acorn is a tiny, fast JavaScript parser, also producing an AST. It is similar to Esprima in terms of functionality but focuses on being smaller and more modular.

cherow

Cherow is a very fast, standards-compliant, self-hosted JavaScript parser with error recovery. It compares to Esprima in terms of compliance and performance but also offers better error handling and recovery options.

README

Esprima (esprima.org) is a high performance, standard-compliant ECMAScript parser written in ECMAScript (also popularly known as JavaScript). Esprima is created and maintained by Ariya Hidayat, with the help of many contributors.

Esprima runs on web browsers (IE 6+, Firefox 1+, Safari 3+, Chrome 1+, Konqueror 4.6+, Opera 8+) as well as Node.js.

Features

• Full support for ECMAScript 5.1(ECMA-262)
• Sensible syntax tree format compatible with Mozilla Parser AST
• Heavily tested (> 550 unit tests with solid 100% statement coverage)
• Optional tracking of syntax node location (index-based and line-column)
• Experimental support for ES6/Harmony (module, class, destructuring, ...)

Esprima is blazing fast (see the benchmark suite). It is up to 3x faster than UglifyJS v1 and it is still competitive with the new generation of fast parsers.

Applications

Esprima serves as the basis for many popular JavaScript development tools:

• Code coverage analysis: node-cover, Istanbul
• Documentation tool: JFDoc, JSDuck
• Language extension: LLJS (low-level JS), Sweet.js (macro)
• ES6/Harmony transpiler: Six, Harmonizr
• Eclipse Orion smart editing (outline view, content assist)
• Source code modification: Esmorph, Code Painter,
• Source transformation: node-falafel, Esmangle, escodegen

Questions?

• Documentation
• Issue tracker: known problems and future plans
• Mailing list
• Contribution guide

Follow @Esprima on Twitter to get the development updates. Feedback and contribution are welcomed!

License

Copyright (C) 2012, 2011 Ariya Hidayat and other contributors.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

• Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.