Javascript validation for file to be uploaded

[Rohan Gavaskar]

How can i validate the file that is to be uploaded? I want that only jpeg file should be uploaded. I know, its simple and many webpages has the solution but.... that method has a loop hole.
That method allows the uploading of any other image type if user just rename that extension by jpeg.
I dont want that.
I want that only real jpeg files should be uploaded
Thanking you in anticipation
Any slightest hint will be appreciated

[Dormilich]

there is no reliable way to determine with JavaScript, whether the file actually is a jpeg.

there are things, that JavaScript is not intended to do and file handling is among them.