readme.hbs

# json-schema-deref

Dereference JSON pointers in a JSON schemas with their true resolved values.
A lighter synchronous version of this module is available as [json-schema-deref-sync](https://github.com/bojand/json-schema-deref-sync),
but omits web references and custom loaders.

## Installation

`npm install json-schema-deref`

## Overview

Let's say you have the following JSON Schema:

```json
{
  "description": "Just some JSON schema.",
  "title": "Basic Widget",
  "type": "object",
  "definitions": {
    "id": {
      "description": "unique identifier",
      "type": "string",
      "minLength": 1,
      "readOnly": true
    }
  },
  "properties": {
    "id": {
      "$ref": "#/definitions/id"
    },
    "foo": {
      "$ref": "http://www.mysite.com/myschema.json#/definitions/foo"
    },
    "bar": {
      "$ref": "bar.json"
    }
  }
}
```

Sometimes you just want that schema to be fully expanded, with `$ref`'s being their (true) resolved values:

```json
{
  "description": "Just some JSON schema.",
  "title": "Basic Widget",
  "type": "object",
  "definitions": {
    "id": {
      "description": "unique identifier",
      "type": "string",
      "minLength": 1,
      "readOnly": true
    }
  },
  "properties": {
    "id": {
      "description": "unique identifier",
      "type": "string",
      "minLength": 1,
      "readOnly": true
    },
    "foo": {
      "description": "foo property",
      "readOnly": true,
      "type": "number"
    },
    "bar": {
      "description": "bar property",
      "type": "boolean"
    }
  }
}
```

This utility lets you do that:


```js
var deref = require('json-schema-deref');
var myschema = require('schema.json');

deref(myschema, function(err, fullSchema) {
  console.dir(fullSchema); // has the full expanded $refs
});
```

## API Reference

{{>all-docs~}}

## Custom Loader

Let's say we want to get $ref's from a MongoDB database, and our `$ref` objects in the JSON Schema might be something like:

```json
"foo": {
  "$ref":"mongodb:507c35dd8fada716c89d0013"
}
```

Our custom loader function passed in the `options` `loader` parameter would look something like:

```js
function myMongoDBLoader(ref, option, fn) {
  if(ref.indexOf('mongodb:') === 0) {
    var id = ref.substring(8);
    return collection.findOne({_id:id}, fn);
  }

  // not ours, pass back nothing to keep it the same
  // or pass error and use failOnMissing to abort
  return fn();
}
```