Using libsyntaqlite from JavaScript

The syntaqlite npm package is libsyntaqlite compiled to WebAssembly, with a JavaScript API. It runs in Node and in the browser. In this tutorial you install it, format a query, check the query against a schema, and look at its syntax tree, using Node.

1. Install

mkdir sql-check && cd sql-check
npm init -y
npm pkg set type=module
npm install syntaqlite

The examples use ES modules and top-level await.

2. Format a query

Create format.js:

import {DialectManager, Engine} from "syntaqlite";

const engine = new Engine();
await engine.load();
await new DialectManager().loadDefault(engine);

process.stdout.write(engine.format("select id,name,email from users where active=1 order by name"));

node format.js

SELECT id, name, email FROM users WHERE active = 1 ORDER BY name;

engine.load() loads the WebAssembly runtime, and loadDefault adds the SQLite dialect. Both are asynchronous, so do them once at startup and reuse the engine.

3. Validate against a schema

Create analyze.js:

import {DialectManager, Engine} from "syntaqlite";

const engine = new Engine();
await engine.load();
await new DialectManager().loadDefault(engine);

const result = engine.analyze("SELECT id, nme FROM users WHERE active = 1", {
  schemaDdl: "CREATE TABLE users (id INTEGER, name TEXT, email TEXT, active INTEGER);",
  strictSchema: true,
});
for (const d of result.diagnostics) {
  console.log(`${d.severity}: ${d.message} (bytes ${d.start_offset}-${d.end_offset})`);
  if (d.help) console.log(`  help: ${d.help}`);
}

node analyze.js

error: unknown column 'nme' (bytes 11-14)
  help: name

strictSchema makes unknown tables and columns errors. Without it, they are reported as warnings. help holds the suggested replacement.

4. Parse and inspect the AST

Create parse.js:

import {DialectManager, Engine} from "syntaqlite";

const engine = new Engine();
await engine.load();
await new DialectManager().loadDefault(engine);

const {statements} = engine.parse("SELECT id, name FROM users WHERE active = 1");
const stmt = statements[0];
console.log(stmt.type);
console.log(stmt.from_clause.type, stmt.from_clause.table_name);
for (const col of stmt.columns.children) {
  console.log(`  ${col.expr.type}: ${col.expr.column}`);
}

node parse.js

SelectStmt
TableRef users
  ColumnRef: id
  ColumnRef: name

parse returns each statement as a plain object, with its node type in type and its fields as properties.

Next steps