simple-json-order/index.js

A lightweight JavaScript utility to preserve the insertion order of top-level keys in JSON objects — ideal for config files, logs, or any use case where key order matters.

export class JSONOrder {
  constructor() {
    this.elements = new Map();
  }

  add(id, value) {
    this.elements.set(String(id), value);
  }

  getAll() {
    return [...this.elements.entries()];
  }

  get(id) {
    return this.elements.get(String(id));
  }

  size() {
    return this.elements.size;
  }

  delete(id) {
    if (id) return this.elements.delete(String(id));
  }

  stringify() {
    let i = 1;
    let mapSize = this.elements.size;
    let jsonString = '';

    if (mapSize > 0) {
      jsonString = '{';

      this.elements.forEach((val, k) => {
        jsonString += `"${k}": ${JSON.stringify(val)}`;

        if (i < mapSize) {
          jsonString += ',';
          i++;
        }
      });

      jsonString += '}';
    }

    return jsonString;
  }

  splitKeyFromValue(str) {
    const result = [];
    let braceDepth = 0;
    let bracketDepth = 0;
    let quote = false;
    let token = '';

    for (let i = 0; i < str.length; i++) {
      const c = str[i];

      if (c === '"' && str[i - 1] !== '\\') {
        quote = !quote;
      } else if (!quote) {
        if (c === '{') braceDepth++;
        if (c === '}') braceDepth--;
        if (c === '[') bracketDepth++;
        if (c === ']') bracketDepth--;
        if (c === ',' && braceDepth === 0 && bracketDepth === 0) {
          result.push(token);
          token = '';
          continue;
        }
      }

      token += c;
    }

    if (token) result.push(token);

    return result;
  }

  parse(json) {
    //Make sure this can be parsed
    try{
      JSON.parse(json);
    }catch(error) {
      console.log(`Error: ${json}`);
      return;
    }
    const finalMap = new Map();
    const inner = json.slice(1, -1).trim();

    if (!inner) return finalMap;

    const pairs = this.splitKeyFromValue(inner);

    for (const pair of pairs) {
      const [keyRaw, valueRaw] = pair.split(/:(.+)/);
      const key = keyRaw.trim().slice(1, -1);
      const value = JSON.parse(valueRaw);

      finalMap.set(key, value);
    }

    this.elements = finalMap;
  }

  prettyStringify() {
    let jsonString = this.stringify();
    let finalString = '';
    let indentLevel = 0;
    let inString = false;

    for (let i = 0; i < jsonString.length; i++) {
      const char = jsonString[i];

      if (char === '"' && jsonString[i - 1] !== '\\') {
        inString = !inString;
      }

      if (!inString) {
        if (char === '{' || char === '[') {
          finalString += char + '\n' + '\t'.repeat(++indentLevel);
          continue;
        }
        if (char === '}' || char === ']') {
          finalString += '\n' + '\t'.repeat(--indentLevel) + char;
          continue;
        }
        if (char === ',') {
          finalString += char + '\n' + '\t'.repeat(indentLevel);
          continue;
        }
        if (char === ':') {
          finalString += ': ';
          continue;
        }
      }

      finalString += char;
    }

    return finalString;
  }
}