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https://github.com/promplate/partial-json-parser-js
Parse partial JSON generated by LLM
https://github.com/promplate/partial-json-parser-js
agent json langchain llm parser prompt-engineering streaming
Last synced: 8 days ago
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Parse partial JSON generated by LLM
- Host: GitHub
- URL: https://github.com/promplate/partial-json-parser-js
- Owner: promplate
- License: mit
- Created: 2023-10-18T10:39:11.000Z (about 1 year ago)
- Default Branch: main
- Last Pushed: 2024-09-17T13:35:34.000Z (2 months ago)
- Last Synced: 2024-11-06T03:04:40.152Z (15 days ago)
- Topics: agent, json, langchain, llm, parser, prompt-engineering, streaming
- Language: TypeScript
- Homepage: https://npmjs.com/package/partial-json
- Size: 15.6 KB
- Stars: 74
- Watchers: 1
- Forks: 2
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# Partial JSON Parser
Sometimes we need **LLM (Large Language Models)** to produce **structural information** instead of natural language. The easiest way is to use JSON.
But before receiving the last token of response, the JSON is broken, which means you can't use `JSON.parse` to decode it. But we still want to stream the data to the user.
Here comes `partial-json`, a lightweight and customizable library for parsing partial JSON strings. Here is a [demo](https://promplate.dev/partial-json-parser).
(Note that there is [a Python implementation](https://github.com/promplate/partial-json-parser) too)
## Installation
```sh
npm i partial-json # or pnpm / bun / yarn
```
`partial-json` is implemented purely in JavaScript, and have both `commonjs` and `esm` builds.
## Usage
### Importing the library
You can import the `parse` function and the `Allow` object from the library like this:
```js
import { parse, Allow } from "partial-json";
```
The `Allow` object is just an Enum for options. It determines what types can be partial. types not included in `allow` only appears after its completion can be ensured.
### Parsing complete / partial JSON strings
The `parse` function works just like the built-in `JSON.parse` when parsing a complete JSON string:
```js
let result = parse('{"key":"value"}');
console.log(result); // Outputs: { key: 'value' }
```
You can parse a partial JSON string by passing an additional parameter to the `parse` function. This parameter is a **bitwise OR** of the constants from the `Allow` object:
(Note that you can directly import the constants you need from `partial-json`)
```js
import { parse, STR, OBJ } from "partial-json";
result = parse('{"key": "v', STR | OBJ);
console.log(result); // Outputs: { key: 'v' }
```
In this example, `Allow.STR` tells the parser that it's okay if a string is incomplete, and `Allow.OBJ` tells the parser so as an object. The parser then try to return as much data as it can.
If you don't allow partial strings, then it will not add `"key"` to the object because `"v` is not close:
```js
result = parse('{"key": "v', OBJ);
console.log(result); // Outputs: {}
result = parse('{"key": "value"', OBJ);
console.log(result); // Outputs: { key: 'value' }
```
Similarity, you can parse partial arrays or even partial special values if you allow it:
(Note that `allow` defaults to `Allow.ALL`)
```js
result = parse('[ {"key1": "value1", "key2": [ "value2');
console.log(result); // Outputs: [ { key1: 'value1', key2: [ 'value2' ] } ]
result = parse("-Inf");
console.log(result); // Outputs: -Infinity
```
### Handling malformed JSON
If the JSON string is malformed, the `parse` function will throw an error:
```js
parse("wrong"); // MalformedJSON [Error]: SyntaxError: Unexpected token 'w', "wrong" is not valid JSON at position 0
```
## API Reference
### parse(jsonString, [allowPartial])
- `jsonString` ``: The JSON string to parse.
- `allowPartial` ``: Specify what kind of partialness is allowed during JSON parsing (default: `Allow.ALL`).
Returns the parsed JavaScript value.
### Allow
An object that specifies what kind of partialness is allowed during JSON parsing. It has the following properties:
- `STR`: Allow partial string.
- `NUM`: Allow partial number.
- `ARR`: Allow partial array.
- `OBJ`: Allow partial object.
- `NULL`: Allow partial null.
- `BOOL`: Allow partial boolean.
- `NAN`: Allow partial NaN.
- `INFINITY`: Allow partial Infinity.
- `_INFINITY`: Allow partial -Infinity.
- `INF`: Allow both partial Infinity and -Infinity.
- `SPECIAL`: Allow all special values.
- `ATOM`: Allow all atomic values.
- `COLLECTION`: Allow all collection values.
- `ALL`: Allow all values.
## Testing
To run the tests for this library, you should clone the repository and install the dependencies:
```sh
git clone https://github.com/promplate/partial-json-parser-js.git
cd partial-json-parser-js
npm i
```
Then, you can run the tests using [Vitest](https://vitest.dev/):
```sh
npm run test
```
Please note that while we strive to cover as many edge cases as possible, it's always possible that some cases might not be covered.
## License
This project is licensed under the MIT License.