module ActiveSupport::JSON

# => "{\"key\":\"<>&\"}"
ActiveSupport::JSON.encode({ key: "<>&" }, escape_html_entities: false)

global escape_html_entities_in_json configuration option.
This can be changed with the +escape_html_entities+ option, or the

# => "{\"key\":\"\\u003c\\u003e\\u0026\"}"
ActiveSupport::JSON.encode({ key: "<>&" })

it escapes <, >, and &:
By default, it also generates JSON that is safe to include in HTML, as

# => "{\"key\":\"\\u2028\"}"
ActiveSupport::JSON.encode({ key: "\u2028" })

U+2028 (Line Separator) and U+2029 (Paragraph Separator):
Generates JSON that is safe to include in JavaScript as it escapes

# => "{\"team\":\"rails\",\"players\":\"36\"}"
ActiveSupport::JSON.encode({ team: 'rails', players: '36' })

See http://www.json.org for more info.
Dumps objects in JSON (JavaScript Object Notation).

def encode(value, options = nil)
  Encoding.json_encoder.new(options).encode(value)
end