How can I add extra parameter to URL when click "apply" button of Views exposed filter? I need to add extra parameter at the end of the page view URL when "apply" button of exposed filter is clicked. 

For example, 

normally URL looks like:

my-view?nid=1


But I need to add "my_parameter=1" at the end of the URL and it eventually needs to be:

my-view?nid=1&amp;my_parameter=1


How can I do this?
You can use a hook_form_FORM_ID_alter() to add a hidden form element with the value that you want (1 in your example). You'll have to check the View name and display name to ensure you only affect the right exposed filter.