(function {})(this, function(){})的(function {})

Question

module.exports怎么理解？(function {})(this, function(){})的(function {})和this参数怎么理解？(function webpackUniversalModuleDefinition(root, factory) {    if(typeof exports === 'object' && typeof module === 'object')        module.exports = factory(require("echarts"));    else if(typeof define === 'function' && define.amd)        define(["echarts"], factory);    else if(typeof exports === 'object')        exports["echarts-gl"] = factory(require("echarts"));    else        root["echarts-gl"] = factory(root["echarts"]);})(this, function(__WEBPACK_EXTERNAL_MODULE_0__) {return /******/ (function(modules) { }

Answer 1

就是一个立刻调用的匿名函数

(function(root,factory){

    //root 因为直接调用所以this是全局对象,浏览器环境为window，node环境为global

    //factory() 返回1

})(this,function(){

    return 1

});

module.exports = factory(require("echarts")); node环境

define(["echarts"], factory); 第三方模块加载插件

root["echarts-gl"]; window环境