Using meta_query with JSON API

example.php

<?php

// 1. The class name must match the filename (i.e., "foo.php" for JSON_API_Foo_Controller)
// 2. Save this in your themes folder
// 3. Activate your controller under Settings > JSON API

class JSON_API_Example_Controller {
  
  public function get_posts_by_meta_query() {
    global $json_api;
    
    if (empty($_GET['meta_query'])) {
      return array(
        'error' => "Specify a 'meta_query' param."
      );
    }
    
    /*
    
    Pass meta_query as URL-encoded JSON
    To borrow the example on http://codex.wordpress.org/Class_Reference/WP_Query
    
    $args = array(
      'meta_query' => array(
        array(
          'key' => 'age',
          'value' => array(3, 4),
          'compare' => 'IN',
        )
      )
    );
    
    Here's how that would look as a URL query param:
    /?json=example/get_posts_by_meta_query&meta_query=%5B%7B%22key%22%3A%22age%22%2C%22value%22%3A%5B3%2C4%5D%2C%22compare%22%3A%22in%22%7D%5D
    
    In JavaScript:
    var meta_query = encodeURIComponent(
      JSON.stringify([
        {
          key: 'age',
          value: [3, 4],
          compare: 'in'
        }
      ])
    );
    
    In PHP:
    $meta_query = rawurlencode(
      json_encode(array(
        'key' => 'age',
        'value' => array(3, 4),
        'compare' => 'IN',
      ))
    );
    
    */
    
    $query = array(
      'ignore_sticky_posts' => true,
      'meta_query' => json_decode($_GET['meta_query'], true)
    );
    return array(
      'posts' => $json_api->introspector->get_posts($query)
    );
  }

}

?>

I have tried to implement this thing..but it looks like its not working. As I am using this using javascript.
I feel instead

 $query = array(
 'ignore_sticky_posts' => true,
 'meta_query' => json_decode($_GET['meta_query'], true)
 );

it should be

$query = array(
  'ignore_sticky_posts' => true,
  'meta_query' => json_decode(stripslashes(rawurldecode($json_api->query->meta_query)), true)
);