cpojer / esprima_ast_explorer

An web tool to explore the AST generated by esprima harmony.

A JavaScript AST explorer

Paste JavaScript code into the editor and inspect the generated AST.

The JavaScript AST explorer provides

• esprima
• espree
• acorn
• babylon
• recast

to parse the code. Depending on the parser settings, it not only supports ES5 but also

• ES6: arrow functions, destructuring, classes, ...
• ES7 propsals: async/await, object rest / spread, ...
• JSX, known through React.
• Typed JavaScript (Flow)

Since future syntax is supported, the JavaScript AST explorer is a useful tool for developers who want to create AST transforms, e.g. with recast. In fact, jscodeshift is included so you can prototype codemodding scripts.

Features

• Save and fork code snippets. Copy the URL to share them.
• Copying an AST or dropping a file containing an AST into the window will parse the AST and update the code using escodegen.
• Otherwise, the content of texteditor will be replaced with the content of the file (i.e. you can drag and drop JS files).
• Choose between multiple parsers and configure them.
• Toggle Transform mode with jscodeshift.
• shift+click on a node expands the full subtree.
• Hovering over a node highlights the corresponding text in the source code:
• Editing the source or moving the cursor around will automatically highlight the corresponding AST node (or its ancestors of it isn't expanded):

Contributions

I'm happy about any feedback, feature request or PR to make this tool as useful as possible!

How to add a new parser

1. Install the new parser as dependency: npm install -S theParser
2. Copy one of the existing examples in src/parsers/.
3. Adjust the code as necessary:

• Load the right parser.
• Call the right parsing method with the right/necessary options.
• Implement the nodeToRange method (this is for highlighting).
• Provide a renderSettings method if applicable.

4. Add a new import to src/parser/index.js.
5. Add the module to partition.json (either as new bundle or to an existing one of there are cross-dependencies).

Build your own version

Install all dependencies with npm install.

Run npm run build for the final minimized version. Run npm run watch for incremental builds.

Run npm start to start a simple static webserver.