json-autocomplete/lib/index.js

Complete unfinished JSON streamed in by LLMs (Like OpenAI's GPT)

const dataCloseChar = {
  "{": "}",
  "[": "]",
  '"': '"',
};

module.exports = (jsonString) => {
  if (!jsonString) return null;

  let string = jsonString
    .trim()
    .replace(/(\r\n|\n|\r|\s{2,})/gm, "")
    .replace(/(?<=:)([a-zA-Z]+)(?=\s*(?![,\}])(?:[,\}\s]|$))/g, " null");

  let missingChars = [];
  for (let i = 0; i < string.length; i++) {
    const char = string[i];
    if (char === missingChars[missingChars.length - 1]) {
      missingChars.pop();
    } else if (dataCloseChar[char]) {
      missingChars.push(dataCloseChar[char]);

      if (char === "{") {
        missingChars.push(":");
      }
    }
  }
  if (missingChars[missingChars.length - 1] === ":") {
    if (string[string.length - 1] !== "{") {
      missingChars[missingChars.length - 1] = ": null";
    } else {
      missingChars.pop();
    }
  }
  const missingCharsString = missingChars.reverse().join("");
  const completeString = string + missingCharsString;
  const cleanedString = completeString
    .replace(/"":/g, "")
    .replace(/":}|": }/g, '": null }')
    .replace(/,""}|,}|,\"\w+\"}/g, "}")
    .replace(/},]/g, "}]");

  return cleanedString;
};