escodegen

What is escodegen?

The escodegen npm package is a code generator that takes an Abstract Syntax Tree (AST) and converts it back into JavaScript code. It is commonly used in the process of developing compilers, code transformers, and other tools that manipulate code structure programmatically.

What are escodegen's main functionalities?

Generating code from an AST

This feature allows you to generate JavaScript code from an AST. The provided code sample demonstrates generating a simple expression '40 + 2' from its AST representation.

const escodegen = require('escodegen');
const ast = {
  type: 'BinaryExpression',
  operator: '+',
  left: { type: 'Literal', value: 40 },
  right: { type: 'Literal', value: 2 }
};
const code = escodegen.generate(ast);
console.log(code); // '40 + 2'

Generating source maps

escodegen can also generate source maps alongside the generated code, which is useful for debugging purposes. The code sample shows how to generate both code and a source map from an AST.

const escodegen = require('escodegen');
const ast = { /* ... */ };
const codeWithSourceMap = escodegen.generate(ast, { sourceMap: true, sourceMapWithCode: true });
console.log(codeWithSourceMap.code); // Generated code
console.log(codeWithSourceMap.map.toString()); // Source map

Custom code generation

You can customize the formatting of the generated code by specifying options such as indentation and newline characters. The code sample illustrates how to generate code with custom formatting options.

const escodegen = require('escodegen');
const ast = { /* ... */ };
const customCode = escodegen.generate(ast, {
  format: {
    indent: {
      style: '  ',
      base: 0
    },
    newline: '\n'
  }
});
console.log(customCode); // Custom formatted code

Other packages similar to escodegen

babel-generator

babel-generator is part of the Babel compiler and is responsible for generating code from Babel's AST. It is similar to escodegen but is more tightly integrated with Babel's ecosystem and plugins.

recast

recast is another code generator that focuses on preserving the original formatting and style of the code as much as possible when generating new code from an AST. It differs from escodegen in its approach to maintaining the original code's readability and structure.

astring

astring is a lightweight and fast code generator for JavaScript, similar to escodegen. It aims to be smaller and faster by focusing on generating code without additional features like source map generation.

README

Escodegen

Escodegen (escodegen) is an ECMAScript (also popularly known as JavaScript) code generator from Mozilla's Parser API AST. See the online generator for a demo.

Install

Escodegen can be used in a web browser:

<script src="escodegen.browser.js"></script>

escodegen.browser.js can be found in tagged revisions on GitHub.

Or in a Node.js application via npm:

npm install escodegen

Usage

A simple example: the program

escodegen.generate({
    type: 'BinaryExpression',
    operator: '+',
    left: { type: 'Literal', value: 40 },
    right: { type: 'Literal', value: 2 }
});

produces the string '40 + 2'.

See the API page for options. To run the tests, execute npm test in the root directory.

Building browser bundle / minified browser bundle

At first, execute npm install to install the all dev dependencies. After that,

npm run-script build

will generate escodegen.browser.js, which can be used in browser environments.

And,

npm run-script build-min

will generate the minified file escodegen.browser.min.js.

License

Escodegen

Copyright (C) 2012 Yusuke Suzuki (twitter: @Constellation) 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.