@lezer/common

Syntax Tree Navigation

This feature allows for navigating through a syntax tree. The code sample demonstrates how to create a cursor from a syntax tree and iterate over its nodes, printing the name of each node's type. This is useful for analyzing or transforming the structure of parsed documents.

let cursor = tree.cursor();
while(cursor.next()) {
  console.log(cursor.node.type.name);
}

Tree Fragment Reuse

Enables efficient parsing by reusing parts of an old syntax tree. The code shows how to apply changes to an array of tree fragments and then use these fragments to assist in parsing a new tree. This significantly improves performance when making incremental updates to a document.

let fragment = TreeFragment.applyChanges(fragments, changes);
let newTree = parser.parse({fragments: [fragment]});

Syntax Node Access

Facilitates direct access to specific nodes within a syntax tree based on position. The example code retrieves a node at a given position (5) and logs its name and the range it spans. This is particularly useful for pinpointing elements in a document for further inspection or modification.

let node = tree.resolve(5);
console.log(node.name, node.from, node.to);