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https://github.com/near/assemblyscript-json

JSON encoder / decoder for AssemblyScript
https://github.com/near/assemblyscript-json

assemblyscript json webassembly

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JSON encoder / decoder for AssemblyScript

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# assemblyscript-json



![npm version](https://img.shields.io/npm/v/assemblyscript-json) ![npm downloads per month](https://img.shields.io/npm/dm/assemblyscript-json)



JSON encoder / decoder for AssemblyScript.



Special thanks to https://github.com/MaxGraey/bignum.wasm for basic unit testing infra for AssemblyScript.



## Installation



`assemblyscript-json` is available as a [npm package](https://www.npmjs.com/package/assemblyscript-json). You can install `assemblyscript-json` in your AssemblyScript project by running:



`npm install --save assemblyscript-json`



## Usage



### Parsing JSON



```typescript

import { JSON } from "assemblyscript-json"; 



// Parse an object using the JSON object

let jsonObj: JSON.Obj = (JSON.parse('{"hello": "world", "value": 24}'));



// We can then use the .getX functions to read from the object if you know it's type

// This will return the appropriate JSON.X value if the key exists, or null if the key does not exist

let worldOrNull: JSON.Str | null = jsonObj.getString("hello"); // This will return a JSON.Str or null

if (worldOrNull != null) {

  // use .valueOf() to turn the high level JSON.Str type into a string

  let world: string = worldOrNull.valueOf();

}



let numOrNull: JSON.Num | null = jsonObj.getNum("value");

if (numOrNull != null) {

  // use .valueOf() to turn the high level JSON.Num type into a f64

  let value: f64 = numOrNull.valueOf();

}



// If you don't know the value type, get the parent JSON.Value

let valueOrNull: JSON.Value | null = jsonObj.getValue("hello");

  if (valueOrNull != null) {

  let value = valueOrNull;



  // Next we could figure out what type we are

  if(value.isString) { 

    // value.isString would be true, so we can cast to a string

    let innerString = (value).valueOf();

    let jsonString = (value).stringify();



    // Do something with string value

  }

}

```



### Encoding JSON



```typescript

import { JSONEncoder } from "assemblyscript-json";



// Create encoder

let encoder = new JSONEncoder();



// Construct necessary object

encoder.pushObject("obj");

encoder.setInteger("int", 10);

encoder.setString("str", "");

encoder.popObject();



// Get serialized data

let json: Uint8Array = encoder.serialize();



// Or get serialized data as string

let jsonString: string = encoder.stringify();



assert(jsonString, '"obj": {"int": 10, "str": ""}'); // True!

```



### Custom JSON Deserializers



```typescript

import { JSONDecoder, JSONHandler } from "assemblyscript-json";



// Events need to be received by custom object extending JSONHandler.

// NOTE: All methods are optional to implement.

class MyJSONEventsHandler extends JSONHandler {

  setString(name: string, value: string): void {

    // Handle field

  }



  setBoolean(name: string, value: bool): void {

    // Handle field

  }



  setNull(name: string): void {

    // Handle field

  }



  setInteger(name: string, value: i64): void {

    // Handle field

  }



  setFloat(name: string, value: f64): void {

    // Handle field

  }



  pushArray(name: string): bool {

    // Handle array start

    // true means that nested object needs to be traversed, false otherwise

    // Note that returning false means JSONDecoder.startIndex need to be updated by handler

    return true;

  }



  popArray(): void {

    // Handle array end

  }



  pushObject(name: string): bool {

    // Handle object start

    // true means that nested object needs to be traversed, false otherwise

    // Note that returning false means JSONDecoder.startIndex need to be updated by handler

    return true;

  }



  popObject(): void {

    // Handle object end

  }

}



// Create decoder

let decoder = new JSONDecoder(new MyJSONEventsHandler());



// Create a byte buffer of our JSON. NOTE: Deserializers work on UTF8 string buffers.

let jsonString = '{"hello": "world"}';

let jsonBuffer = Uint8Array.wrap(String.UTF8.encode(jsonString));



// Parse JSON

decoder.deserialize(jsonBuffer); // This will send events to MyJSONEventsHandler

```



Feel free to look through the [tests](https://github.com/nearprotocol/assemblyscript-json/tree/master/assembly/__tests__) for more usage examples.



## Reference Documentation



Reference API Documentation can be found in the [docs directory](./docs).



## License



[MIT](./LICENSE)