How to validate a file upload field using Javascript/jquery

Question

How can I validate if the user has selected a file to upload?

Edit: bumped

Answer 1

My function will check if the user has selected the file or not and you can also check whether you want to allow that file extension or not.

Try this:

function validate_fileupload(fileName)
{
    var allowed_extensions = new Array("jpg","png","gif");
    var file_extension = fileName.split('.').pop().toLowerCase(); // split function will split the filename by dot(.), and pop function will pop the last element from the array which will give you the extension as well. If there will be no extension then it will return the filename.

    for(var i = 0; i <= allowed_extensions.length; i++)
    {
        if(allowed_extensions[i]==file_extension)
        {
            return true; // valid file extension
        }
    }

    return false;
}