如何检查文件的扩展名并验证从谷歌驱动器上传的文件

I have a select tag which has 3 options, powerpoint,pdf and spreadsheet and I am uploading it from google drive which is not validated, that means if I give ppt link to pdf option it is uploading. Please help me to validate it.I have a select tag which has 3 options, powerp