lang/js/README.md

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# Avro-js

Pure JavaScript implementation of the [Avro specification](https://avro.apache.org/docs/current/spec.html).


## Features

+ Fast! Typically twice as fast as JSON with much smaller encodings.
+ Full Avro support, including recursive schemas, sort order, and evolution.
+ Serialization of arbitrary JavaScript objects via logical types.
+ Unopinionated 64-bit integer compatibility.
+ No dependencies, `avro-js` even runs in the browser.


## Installation

```bash
$ npm install avro-js
```

`avro-js` is compatible with all versions of [node.js][] since `0.11` and major
browsers via [browserify][].


## Documentation

See `doc/` folder.


## Examples

Inside a node.js module, or using browserify:

```javascript
var avro = require('avro-js');
```

+ Encode and decode objects:

  ```javascript
  // We can declare a schema inline:
  var type = avro.parse({
    name: 'Pet',
    type: 'record',
    fields: [
      {name: 'kind', type: {name: 'Kind', type: 'enum', symbols: ['CAT', 'DOG']}},
      {name: 'name', type: 'string'}
    ]
  });
  var pet = {kind: 'CAT', name: 'Albert'};
  var buf = type.toBuffer(pet); // Serialized object.
  var obj = type.fromBuffer(buf); // {kind: 'CAT', name: 'Albert'}
  ```

+ Generate random instances of a schema:

  ```javascript
  // We can also parse a JSON-stringified schema:
  var type = avro.parse('{"type": "fixed", "name": "Id", "size": 4}');
  var id = type.random(); // E.g. Buffer([48, 152, 2, 123])
  ```

+ Check whether an object fits a given schema:

  ```javascript
  // Or we can specify a path to a schema file (not in the browser):
  var type = avro.parse('./Person.avsc');
  var person = {name: 'Bob', address: {city: 'Cambridge', zip: '02139'}};
  var status = type.isValid(person); // Boolean status.
  ```

+ Get a [readable stream][readable-stream] of decoded records from an Avro
  container file (not in the browser):

  ```javascript
  avro.createFileDecoder('./records.avro')
    .on('metadata', function (type) { /* `type` is the writer's type. */ })
    .on('data', function (record) { /* Do something with the record. */ });
  ```

+ Implement recursive schemata (due to lack of duck-typing):

  ```javascript
    // example type: linked list with one long-int as element value
    const recursiveRecordType =  avro.parse({
      "type": "record",
      "name": "LongList",
      "fields" : [
        {"name": "value", "type": "long"},             
        {"name": "next", "type": ["null", "LongList"]} // optional next element via recursion
      ]
    });

    // will work
    const validRecursiveRecordDTO = {
      value: 1,
      next: {
        // no duck-typing support: from first nested level on the 
        // recursive type has to be explicitly specified.
        LongList: {
          value: 2,
          next: null
        }
      }
    };
    const serializedValid = recursiveRecordType.parse(validRecursiveRecordDTO);
    

    // will throw error
    const invalidRecursiveRecordDTO = {
      value: 1,
      next: {
          value: 2,
          next: null
      }
    };
    const serializedInvalid = recursiveRecordType.parse(invalidRecursiveRecordDTO);


  ```


[node.js]: https://nodejs.org/en/
[readable-stream]: https://nodejs.org/api/stream.html#stream_class_stream_readable
[browserify]: http://browserify.org/