JS snippet to empty all messages from LinkedIn's UI.

empty_linkedin_inbox.js

/*
  This function can be used to empty your
  LinkedIn inbox. You should first scroll
  to the bottom of the list, so that it
  lazy-loads all of your messages into
  the DOM at once. Then run this…
*/

// Closure.
(function ($) {
  // Extract security token.
  var token =
  $('a[href*="csrfToken="]')
    .attr('href')
    .split('csrfToken=')[1]
    .split('&')[0]

  // Loop through delete links.
  $('.delete-action').each(function () {
    // Get unique message ID.
    var id =
    $(this)
      .closest('.thread-preview')
      .find('[data-id]')
      .attr('data-id')

    // Build URL.
    var url = [
      '/messaging/conversations/',
      id,
      '?csrfToken=',
      token
    ].join('')

    // Send the request.
    $.ajax({
      url: url,
      type: 'DELETE'
    })
  })

// Pass jQuery into scope.
})(this.jQuery)