# PageDataService¶

The page data service is responsible for collecting additional data about a page. This could include information about the media on a page, product information, etc. When enabled it will automatically try to find page data for pages that the user browses or it can be directed to asynchronously look up the page data for a url.

The PageDataService is an EventEmitter and listeners can subscribe to its notifications via the on and once methods.

The service can be enabled by setting browser.pagedata.enabled to true. Additional logging can be enabled by setting browser.pagedata.log to true.

## PageData Data Structure¶

At a high level the page data service can collect many different kinds of data. When queried the service will respond with a PageData structure which holds some general information about the page, the time when the data was discovered and a map of the different types of data found. This map will be empty if no specific data was found. The key of the map is from the PageDataSchema.DATA_TYPE enumeration. The value is the JSON data which differs in structure depending on the data type.

{
"url": <url of the page as a string>,
"date": <epoch based timestamp>,
"siteName": <a friendly name for the website>,
"image": <url for an image for the page as a string>,
"data": <map of data types>,
}


## PageData Collection¶

Page data is gathered in one of two ways.

Page data is automatically gathered for webpages the user visits. This collection is trigged after a short delay and then updated when necessary. Any data is cached in memory for a period of time. When page data has been found a page-data event is emitted. The event’s argument holds the PageData structure. The getCached function can be used to access any cached data for a url.

## Supported Types of page data¶

The following types of page data (PageDataSchema.DATA_TYPE) are currently supported:

• PRODUCT

• DOCUMENT

• ARTICLE

• AUDIO

• VIDEO