@qraftr/json-repair

A small but powerful utility to repair broken JSON strings - especially useful when dealing with LLM output or hand-written JSON.
Need to repair JSON? This tool automatically fixes malformed or broken JSON structures with a single function call. Works seamlessly with both TypeScript and JavaScript (ESM & CommonJS).

Features

• Fixes:
  • Unquoted keys
  • Unquoted string values
  • Trailing commas
  • Missing commas between values
  • Missing colons between keys and values
  • Invalid literals (NaN, undefined, Infinity)
  • Capitalized literals (True, False, Null)
  • Single quotes
  • Line and block comments
  • Unclosed strings in noisy input
  • Missing closing braces
  • Misplaced quotes inside strings
  • LLM code blocks (e.g. json ... )
  • LLM JSON extraction (e.g. The result is: {...})
• Auto-extracts JSON blocks from surrounding text as a fallback
• Option to return a string or JS object
• ASCII escaping (converts non-ASCII characters to \uXXXX)
• Safe fallback mode

Install

pnpm add @qraftr/json-repair

Or with npm:

npm install @qraftr/json-repair

Example usage

TypeScript

import { repairJson } from "@qraftr/json-repair";

const input = `{name: Seb, age: 42,}`;
const repaired = repairJson(input);
console.log(repaired);
// {"name":"Seb","age":42}

JavaScript (CommonJS)

const { repairJson } = require("@qraftr/json-repair");

console.log(repairJson("{name: Seb, age: 42,}"));

JavaScript (ESM)

import { repairJson } from "@qraftr/json-repair";

console.log(repairJson("{name: Seb, age: 42,}"));

Options

| Option | Type | Default | Description | | ------------------------ | ------- | ------- | ----------------------------------------------------------------- | | extractJson | boolean | false | Extract the first JSON block up front from surrounding text | | disableExtractFallback | boolean | false | Disable the automatic fallback extraction when parsing fails | | encodeAscii | boolean | false | Escape non-ASCII characters to \uXXXX | | returnObject | boolean | false | Return a JS object instead of a JSON string | | logging | boolean | false | Enable console logs of each transformation step | | safeMode | boolean | false | Throw a friendly error instead of crashing on unrecoverable input |

Automatic fallback: if parsing fails (or yields only a primitive) and a JSON block is found inside the input, it will be extracted and repaired unless disableExtractFallback is set to true.

Examples

| Input | Output | | ----------------------------------- | ---------------------------------- | | {name: Seb} | {"name":"Seb"} | | {user: {name: Seb, age: 30}} | {"user":{"name":"Seb","age":30}} | | {value: NaN} | {"value":null} | | Intro... {name: Seb} ...outro | {"name":"Seb"} | | Hello!\n\n\``json\n{name: Seb}|{"name":"Seb"}` |

Live demonstration

Try it: Qraftr Libs

Motivation

This package was designed to help deal with malformed JSON, especially the kind you get from LLMs like ChatGPT and OpenAI APIs when asking for json output. This package is ideal if you're looking to repair JSON, fix malformed JSON, or sanitize AI-generated output. It can also be used to quickly recover and parse broken logs or hand-crafted config files.

Author

Made by @Sebog33
Follow Qraftr Libs for more tiny dev-focused utilities.

License

MIT