JavaScript AST Explorer Lite

Parse JavaScript or TypeScript locally into an interactive ESTree syntax tree. Collapse nodes and select any node to highlight its source range. Inputs must be smaller than 100,000 UTF-8 bytes.

Ast Explorer Lite · Client runtimeSandboxed

Ast Explorer Lite Input

Ast Explorer Lite Output

Formatted results will render here in real time.

Ast Explorer Lite: JavaScript is required to run this tool in the browser.

About this javascript ast explorer lite

Parse JavaScript or TypeScript locally into an interactive ESTree syntax tree. Collapse nodes and select any node to highlight its source range. Inputs must be smaller than 100,000 UTF-8 bytes Transforms and validates developer data structures locally, preventing confidential payload exposure during data wrangling.

Syntax parsing & data transformation logic

Parses JavaScript and TypeScript locally and returns an interactive ESTree-shaped tree with exact source ranges.

Worked conversion & output example

Scenario: A compiler student inspects the ESTree Abstract Syntax Tree (AST) produced by a JavaScript statement.

Sample input:

const answer = 42;

Processing: The JSON below is an excerpt: other fields and nodes are omitted. Select Identifier to highlight answer at UTF-16 offsets 6–12.

Illustrative output:

{ "type": "Program", "sourceType": "script", "body": [ { "type": "VariableDeclaration", "kind": "const", "declarations": [ { "type": "VariableDeclarator", "id": { "type": "Identifier", "name": "answer", "range": [ 6, 12 ] }, "init": { "type": "Literal", "value": 42, "raw": "42" } } ] } ] }

Syntax constraints & input size limits

Uses the TypeScript parser locally and displays a practical ESTree-shaped tree with source ranges. TypeScript-specific declarations and type nodes use TS-prefixed ESTree extensions. No source is sent to a server; input must be below 100,000 UTF-8 bytes. The parser is TypeScript 5.9.3 (Apache-2.0); using this tool is free. Once the page reports that the parser is ready, this loaded page can parse offline.

Data conversions and formatting in JavaScript AST Explorer Lite reflect standard structured syntax. Verify parsed outputs against your target runtime before deployment.

Local client execution boundary

Data parsing and transformations in JavaScript AST Explorer Lite execute in the local browser tab without remote data transmission.

Data format specifications & language standards

Data interchange formats and language grammar specifications:

JavaScript AST Explorer Lite verification · Audit standards

How to use it

Enter JavaScript or TypeScript source code below 100,000 UTF-8 bytes.
Parse locally with the TypeScript compiler parser and inspect the ESTree-shaped syntax tree.
Collapse branches or select a node to highlight its exact source range.

Frequently asked questions

What does AST Explorer Lite parse?+

It uses the TypeScript parser locally to create an ESTree-shaped syntax tree for JavaScript and TypeScript source. TypeScript-only declarations and types are represented with TS-prefixed extension nodes.

How can I inspect a node in the source?+

Expand or collapse branches in the syntax tree. Select a node to highlight its start-to-end source range in the editor.

What source limit applies?+

The input must be smaller than 100,000 UTF-8 bytes. The byte counter uses UTF-8, so multibyte characters count according to their encoded size.

Is source code sent to a server?+

No. Parsing runs locally in the browser; source text is not sent to a server.