javascript自执行function

我无法理解这个function。 我了解身体的一部分。 但是，为什么function全球化，出口之后呢？

(function(global) { "use strict;" // Class ------------------------------------------------ var Config = {}; Config.host = "45.55.81.215"; Config.port = 80; Config.urlPrefix = '/spika'; Config.socketNameSpace = '/spika'; Config.imageDownloadURL = "http://" + Config.host + "/:" + Config.port + Config.urlPrefix + "/media/images/"; Config.noavatarImg = "http://" + Config.host + ":" + Config.port + Config.urlPrefix + "/img/noavatar.png"; Config.chatDatabaseUrl = "mongodb://localhost/simplemessenger"; Config.dbCollectionPrefix = "spika_"; Config.uploadDir = 'public/uploads/'; Config.sendAttendanceMessage = true; Config.stickerBaseURL = 'http://spika.chat'; Config.stickerAPI = Config.stickerBaseURL + '/api/v2/stickers/56e005b1695213295419f5df'; // Exports ---------------------------------------------- module["exports"] = Config; })((this || 0).self || global);