fastparselite/v1/parser.js

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

const fs = require("fs");

function removeComments(text) {
  return text
    .split("\n")
    .map(line => line.replace(/(#|\/\/).*/, "").trim())
    .filter(line => line.length > 0)
    .join("\n");
}

function parseObjectBlock(content) {
  const obj = {};
  let i = 0;

  while (i < content.length) {
    while (content[i] === "\n" || content[i] === " ") i++;

    const keyMatch = content.slice(i).match(/^(\w+):/);
    if (!keyMatch) break;

    const key = keyMatch[1];
    i += key.length + 1;

    while (content[i] === " " || content[i] === "\n") i++;

    // Nested object
    if (content[i] === "{") {
      let depth = 1;
      let j = i + 1;
      while (j < content.length && depth > 0) {
        if (content[j] === "{") depth++;
        else if (content[j] === "}") depth--;
        j++;
      }

      const inner = content.slice(i + 1, j - 1);
      obj[key] = parseObjectBlock(inner.trim());
      i = j;

      // Move to next line after closing }
      while (content[i] === "\n" || content[i] === " ") i++;
    }
    // Array
    else if (content[i] === "[") {
      let j = i + 1;
      while (j < content.length && content[j] !== "]") j++;
      const inner = content.slice(i + 1, j);
      obj[key] = inner.split(",").map(s => s.trim());
      i = j + 1;
    }
    // Primitive
    else {
      let j = i;
      while (j < content.length && content[j] !== "\n" && content[j] !== "\r") j++;
      let value = content.slice(i, j).trim();

      if (value.startsWith('"') && value.endsWith('"')) {
        value = value.slice(1, -1);
      } else if (value === "true") {
        value = true;
      } else if (value === "false") {
        value = false;
      } else if (!isNaN(value)) {
        value = Number(value);
      }

      obj[key] = value;
      i = j + 1;
    }
  }

  return obj;
}

function parseLiteData(text) {
  const cleanText = removeComments(text);
  const data = {};
  const blocks = cleanText.match(/@(\w+)\s*{([\s\S]*?)}/g);

  if (!blocks) return data;

  for (const block of blocks) {
    const [, name, content] = block.match(/@(\w+)\s*{([\s\S]*)}/);
    data[name] = parseObjectBlock(content.trim());
  }

  return data;
}

function flatten(obj, prefix = "", result = {}) {
  for (const key in obj) {
    const value = obj[key];
    const newKey = prefix ? `${prefix}_${key}` : key;
    if (typeof value === "object" && !Array.isArray(value)) {
      flatten(value, newKey, result);
    } else {
      result[newKey] = value;
    }
  }
  return result;
}

// ======== Usage =========
const input = fs.readFileSync("sample.ld", "utf8");
const result = parseLiteData(input);

const flatUser = flatten(result.user);
// console.log("User name:", flatUser.name);
console.log("User active:", flatUser.active);
console.log("User address city:", flatUser.address_description);
// console.log("User address wait:", flatUser.address_wait);
// console.log("Latitude:", flatUser.address_location_lat);