How do I validate if a file is selected for upload before submitting a form , using jquery validator

I have a page in my web application where there is an option to upload a file. I am trying to validate if there is a file selected for upload, before submitting the form. I use jQuery form validator plugin for my form validations.

My html code for the file input tag is:

<div class="form-group">
 <label for="exampleInputFile">New File</label>
 <input type="file" id="file_add" name="file">                                         
</div>

I am trying to check if there is any file selected using the following code:

$.formUtils.addValidator({
      name : 'file_check',
      validatorFunction : function(value, $el, config, language, $form) 
      {
      if($('#addFile').val() == "")
        return $('#file_add').val() == "" == 0;
      },
      errorMessage : 'Please choose a file',
      errorMessageKey: 'notConfirmed'
    });

But the form submission is still happening even if there is no file chosen for upload. Is there any way I can check if there is a file selected before the submission happens.....