Swicth basemap not working

Question

Can anybody tell me why this sample works if we run it from esri's website but it does not work if we download and run it from our computer?

https://developers.arcgis.com/en/javascript/jssamples/widget_basemap.html

kenbuja · Accepted Answer

It probably will not run properly if you copy it to you computer and double click on it (meaning the browser shows the url something like file:///C:/Users/me/Desktop/index.html). You to set up a development environment. When developing with the ArcGIS API for JavaScript, a web server is  required. This means that web pages and apps using the ArcGIS API for  JavaScript need to be accessed over http://  (or https://) rather than file://. To meet this requirement, install  and configure a web server. Web server software is available free of  charge for all operating systems. For Windows, IIS is recommended. On Mac OS and Linux, Apache  is a popular option but any web server will do. The important point is  web pages using the ArcGIS API for JavaScript are served over http.