bottaiko/node_modules/mimic-response/index.js

'use strict';

// We define these manually to ensure they're always copied
// even if they would move up the prototype chain
// https://nodejs.org/api/http.html#http_class_http_incomingmessage
const knownProperties = [
	'aborted',
	'complete',
	'destroy',
	'headers',
	'httpVersion',
	'httpVersionMinor',
	'httpVersionMajor',
	'method',
	'rawHeaders',
	'rawTrailers',
	'setTimeout',
	'socket',
	'statusCode',
	'statusMessage',
	'trailers',
	'url'
];

module.exports = (fromStream, toStream) => {
	const fromProperties = new Set(Object.keys(fromStream).concat(knownProperties));

	for (const property of fromProperties) {
		// Don't overwrite existing properties.
		if (property in toStream) {
			continue;
		}

		toStream[property] = typeof fromStream[property] === 'function' ? fromStream[property].bind(fromStream) : fromStream[property];
	}

	return toStream;
};