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A JS Foundation Project

Events

Events

Information is shared internally via events. connectors and parsers can create them, while parsers and hints consume them. To add new events via a parser, you must export a type defining the event names and expected values.

// example.ts
import { Event, Events } from 'hint/dist/src/lib/types/events';
...
export type StyleParse = Event & {
ast: Root;
};

export type StyleEvents = Events & {
'parse::end::css': StyleParse;
'parse::start::css': Event;
};

export default class CSSParser extends Parser<StyleEvents> {
public constructor(engine: Engine<StyleEvents>) {
super(engine, 'css');
...
}
...
}

The following is a list of all the events common to all connectors, with their signature, and the interface they implement. The exception is the local connector that needs the HTML parser to emit these events:

For additional events emitted by specific parsers (e.g. parse::end::css), see parsers.

element::<element-type>

Event is emitted when the connector visits an element in the DOM when traversing it. <element-type> is the nodeName lower cased.

Format:

type ElementFound = {
/** The URI of the resource firing this event. */
resource: string;
/** The visited element. */
element: IAsyncHTMLElement;
}

fetch::end::<resource-type>

Event is emitted when the content of a resource (js, css, image, etc.) has finished downloading.

Format:

type FetchEnd {
/** The element that initiated the request. */
element: IAsyncHTMLElement;
/** The URL of the target */
resource: string;
/** The request made to fetch the target. */
request: Request;
/** The response sent while fetching the target. */
response: Response;
}

fetch::error::<resource-type>

Event is emitted when a problem downloading the content of a resource was encountered.

Format:

type FetchError {
/** The URL of the target. */
resource: string;
/** The element that initiated the request. */
element: IAsyncHTMLElement;
/** The error found. */
error: any;
/** The redirects performed for the url. */
hops: string[];
}

fetch::start::<resource-type>

Event is emitted when the request to fetch the target is about to start

Format:

type FetchStart {
/** The URL to download */
resource: string;
}

scan::end

Event is emitted when the connector has finished sending all events and its about to return. This is the last event to be emitted.

Format:

type ScanEnd {
/** The final URL analyzed. */
resource: string;
}

scan::start

Event is emitted when the connector is about to start the analysis. This is the first event to be emitted.

Format:

type ScanStart {
/** The URL to analyze. */
resource: string;
}

Note: This event is fired synchronously. You should not return a Promise because it will not wait for it to be resolved. If you need to perform an async operation you should combine it with scan::end. You can find more information in how to interact with other services.

traverse::down

Event is emitted when the connector is traversing and starts visiting the children of a node. element is the parent node that is to be traversed.

Format:

type TraverseDown {
/** The parent element to be traversed. */
element: IAsyncHTMLElement;
/** The URL of the target. */
resource: string;
}

traverse::end

Event is emitted when the connector has finished traversing the DOM entirely.

Format:

type TraverseEnd {
/** The URL of the target. */
resource: string;
}

traverse::start

Event is emitted when the connector is going to start traversing the DOM.

Format:

type TraverseStart {
/** The URL of the target. */
resource: string;
}

traverse::up

Event is emitted when the connector has finsihed visiting the children of a node and goes to the next one. element is the parent node that was traversed.

Format:

type TraverseUp {
/** The parent element that was traversed. */
element: IAsyncHTMLElement;
/** The URL of the target. */
resource: string;
}

can-evaluate::script

Event is emitted when the connector is ready to evaluate scripts.

type CanEvaluateScript {
/** The URL of the target. */
resource: string;
}