fastparselite/v2/parser.js

Super simple & fast DSL parser for lightweight config-like data using custom syntax.

function fastParseLite(text) {
  const lines = text.split('\n').map(l => l.trim()).filter(l => l.length && !l.startsWith("//") && !l.startsWith("#"));
  const stack = [{}];
  let current = stack[0];

  for (let line of lines) {
    if (line.endsWith('{')) {
      const key = line.slice(0, -1).trim();
      const newObj = {};
      current[key] = newObj;
      stack.push(current);
      current = newObj;
    } else if (line === '}') {
      current = stack.pop();
    } else {
      const [key, rawVal] = line.split('=').map(s => s.trim());
      let val;

      if (rawVal.startsWith('#')) {
        val = Number(rawVal.slice(1));
      } else if (rawVal.startsWith('!')) {
        val = rawVal.slice(1) === 'true';
      } else {
        val = rawVal;
      }

      current[key] = val;
    }
  }

  return stack[0];
}

const input = `
user{
  name=Alice
  age=#25
  address{
    city=New York
    zip=#10001
  }
  active=!true
}
`;

const result = fastParseLite(input);
console.log(result.user.address.city); // New York