Ajax验证表单$ _FILES ['ImageFile']

Hey guys i been trying all day to find a way to validate some upload files using javascript

// get values from FORM
        var firstname = $("input#firstname").val();
        var lastname = $("input#lastname").val();
        var username = $("input#username").val();
        var ImageFile= $("file#ImageFile").val();
        var email = $("input#email").val();
        var message = $("textarea#message").val();
        var firstName = name; 
        if (firstName.indexOf(' ') >= 0) {
            firstName = name.split(' ').slice(0, -1).join(' ');
        }
        $.ajax({
            url: "mail/contact_me.php",
            type: "POST",
            data: {
                firstname: firstname,
                lastname: lastname,
                username: username,
                ImageFile: ImageFile,
                email: email,
                message: message
            },
            cache: false,

If i remove the var ImageFILE = $("file#ImageFile").val(); the script work i need this to send a attachment with phpmailer my php is working my form is working great but if i try adding the java just die i think im doing something wrong here i never was really good on java any subjection?

The email is sent but the attachment is not getting there