angular2 – systemjs.config.js在角度2包装结构中做什么？

(function(global) {

      // map tells the System loader where to look for things
      var map = {
        'app':                        'app',// 'dist','rxjs':                       'node_modules/rxjs','angular2-in-memory-web-api': 'node_modules/angular2-in-memory-web-api','@angular':                   'node_modules/@angular','primeng':                        'node_modules/primeng'
      };

      // packages tells the System loader how to load when no filename and/or no extension
      var packages = {
        'app':                        { main: 'boot.js',defaultExtension: 'js' },'rxjs':                       { defaultExtension: 'js' },'angular2-in-memory-web-api': { defaultExtension: 'js' },'primeng':                    { defaultExtension: 'js' }
      };

      var packagenames = [
        '@angular/common','@angular/compiler',//
      ];

      // add package entries for angular packages in the form '@angular/common': { main: 'index.js',defaultExtension: 'js' }
      packagenames.forEach(function(pkgName) {
        packages[pkgName] = { main: 'index.js',defaultExtension: 'js' };
      });

      var config = {
        map: map,packages: packages
      }

      // filterSystemConfig - index.html's chance to modify config before we register it.
      if (global.filterSystemConfig) { global.filterSystemConfig(config); }

      System.config(config);

    })(this);