how to read a text file using Javascript

Question

I am taking a text file from user and then posting that file back to the browser using ajax storing the content in db and then showing the content back to user page using Jquery post response. Now i want to something like this..

Read the text file from the user computer using javascript. Display the content and when he submits the page I will save the values.

Answer 1

Can't be done in pure JS for security reasons. You would need to have the user upload the file to your server, and fetch the contents back through Ajax.

If you use Flash or Java, you should be able to gain direct access to the file. If you speak Flash/Actionsript, maybe SWFUpload 's source code (especially the new client-side resizing functions) can serve as an inspiration.

Update: This blog entry should help. Read and write local files with Flash Player 10

Update: To elaborate on the "upload and fetch" thing, if you do the uploading in an IFRAME , you could even have the upload script simply output the text file's contents. Because the iframe belongs to your domain, you will be able to retrieve its contents via JavaScript when the upload has finished. As long as you send a content-type: application/text it should be fairly safe from any malicious attacks.

Answer 2

如果您对Firefox 3.6的支持还可以，请仅查看https://developer.mozilla.org/en/Using_files_from_web_applications ，否则，您应该使用Flash，Java或silverlight。

Answer 3

Reading client files in javascript is possible with the new File API available in modern browsers. Check this site and its code: http://www.readfileonline.com/

However, before reading file contents in javascript, the user must explicitly select the files it allows to read. This is a security feature of the standard.

Answer 4

由于安全问题，您将无法读取用户计算机中的文件。