This module provides Node.js bindings to the [tree-sitter] parsing library.
npm install tree-sitterFirst, you'll need a Tree-sitter grammar for the language you want to parse. There are many existing grammars, such as tree-sitter-javascript. These grammars can typically be installed with a package manager like NPM, so long as the author has published them.
npm install tree-sitter-javascriptYou can also develop a new grammar by using the Tree-sitter CLI and following the docs.
Once you've got your grammar, create a parser with that grammar.
const Parser = require('tree-sitter'); const JavaScript = require('tree-sitter-javascript'); const parser = new Parser(); parser.setLanguage(JavaScript);Then you can parse some source code,
const sourceCode = 'let x = 1; console.log(x);'; const tree = parser.parse(sourceCode);and inspect the syntax tree.
console.log(tree.rootNode.toString()); // (program // (lexical_declaration // (variable_declarator (identifier) (number))) // (expression_statement // (call_expression // (member_expression (identifier) (property_identifier)) // (arguments (identifier))))) const callExpression = tree.rootNode.child(1).firstChild; console.log(callExpression); // { // type: 'call_expression', // startPosition: {row: 0, column: 16}, // endPosition: {row: 0, column: 30}, // startIndex: 0, // endIndex: 30 // }If your source code changes, you can update the syntax tree. This is much faster than the first parse.
// In the code, we replaced 'let' with 'const'. // So, we set our old end index to 3, and our new end index to 5. // Note that the end index is exclusive. const newSourceCode = 'const x = 1; console.log(x);'; // ^ ^ // indices: 3 5 // points: (0,3) (0,5) tree.edit({ startIndex: 0, oldEndIndex: 3, newEndIndex: 5, startPosition: {row: 0, column: 0}, oldEndPosition: {row: 0, column: 3}, newEndPosition: {row: 0, column: 5}, }); const newTree = parser.parse(newSourceCode, tree);If your text is stored in a data structure other than a single string, such as a rope or array, you can parse it by supplying a callback to parse instead of a string:
const sourceLines = [ 'let x = 1;', 'console.log(x);' ]; const tree = parser.parse((index, position) => { let line = sourceLines[position.row]; if (line) { return line.slice(position.column); } });It's recommended that you read the Tree-sitter documentation on using parsers to get a higher-level overview of the API. Once you're comfortable with the basics, you can explore the full API documentation, which should map closely to the C API, though there are some differences.
