Regular expressions to validate file extension before file upload in javascript using asp.net

Validate file extension before file upload in javascript using asp.net by Regular expressions 

this article ,I will explain how to cheak or validate file in file upload control using javascript and regular expression to cheak file extension before file upload using Javascript in ASP.NET.

Here I have some of regular expressions to validate file upload. 

Regular expression to validate file formats for .mp3 or .MP3 or .mpeg or .MPEG or m3u or M3U Re= /^(([a-zA-Z]:)|(\\{2}\w+)\$?)(\\(\w[\w].*))+(.mp3|.MP3|.mpeg|.MPEG|.m3u|.M3U)$/; Regular expression to validate file formats for .doc or .docx Re= /^(([a-zA-Z]:)|(\\{2}\w+)\$?)(\\(\w[\w].*))+(.doc|.docx|.DOC|.DOCX)$/; Regular expression to validate file formats for .txt or .TXT Re= /^(([a-zA-Z]:)|(\\{2}\w+)\$?)(\\(\w[\w].*))+(.txt|.TXT)$/; Regular expression to validate file formats for .jpeg or .JPEG or .gif or .GIF or .png or .PNG Re= /^(([a-zA-Z]:)|(\\{2}\w+)\$?)(\\(\w[\w].*))+(.jpeg|.JPEG|.gif|.GIF| .png|.PNG)$/;