DefinitelyTyped/types/on-headers/index.d.ts

// Type definitions for on-headers 1.0
// Project: https://github.com/jshttp/on-headers
// Definitions by: John Jeffery <https://github.com/jjeffery>
//                 BendingBender <https://github.com/BendingBender>
// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped

/// <reference types="node" />

import { ServerResponse } from 'http';

/**
 * This will add the listener to fire when headers are emitted for res.
 * The listener is passed the response object as its context (this).
 * Headers are considered emitted only once, right before they
 * are sent to the client.
 *
 * When this is called multiple times on the same res, the listeners
 * are fired in the reverse order they were added.
 *
 * @param res HTTP server response object
 * @param listener Function to call prior to headers being emitted,
 *        the response object is passed as this context.
 */
declare function onHeaders(res: ServerResponse, listener: (this: ServerResponse) => void): void;

export = onHeaders;