The ESTree Spec
Once upon a time, an unsuspecting Mozilla engineer created an API in Firefox that exposed the SpiderMonkey engine's JavaScript parser as a JavaScript API. Said engineer documented the format it produced, and this format caught on as a lingua franca for tools that manipulate JavaScript source code.
Meanwhile JavaScript is evolving. This site will serve as a community standard for people involved in building and using these tools to help evolve this format to keep up with the evolution of the JavaScript language.
Discussion
We've started the process of bringing together various communities using this format to move it forward into the ES2015 era and beyond. Feel free to join us! We'll be discussing in the issue tracker and in #esprima on Freenode.
AST Descriptor Syntax
The spec uses a custom syntax to describe its structures. For example, at the
time of writing, 'es2015.md' contained a description of Program as seen below
extend interface Program {
sourceType: "script", "module";
body: [ Statement, ModuleDeclaration ];
}
Participating Members
- Dave Herman (Mozilla)
- Ingvar Stepanyan, Adrian Heine (Acorn)
- Nicholas C. Zakas (ESLint)
- Ariya Hidayat (Esprima)
- Michael Ficarra (@michaelficarra)
- Henry Zhu, Logan Smyth, Daniel Tschinder (Babel)
Inactive Members
- Sebastian McKenzie (Babel)
- Kyle Simpson (@getify)
- Mike Sherov (Esprima)
Philosophy
Suggested additions and modifications must follow these guidelines:
- Backwards compatible: Non-additive modifications to existing constructs will not be considered unless immense support is in favor of such changes. (eg. #65)
- Contextless: Nodes should not retain any information about their parent. ie. a
FunctionExpressionshould not be aware of if it's a concise method. (eg. #5) - Unique: Information should not be duplicated. ie. a
kindproperty should not be present onLiteralif the type can be discerned from thevalue. (eg. #61) - Extensible: New nodes should be specced to easily allow future spec additions. This means expanding the coverage of node types. ie.
MetaPropertyoverNewTargetto cover future meta properties. (eg. #32)