Depois eu explico.

close-on-click-out.js

$(document).ready(function(){
  // Event Click in whatever tag HTML
  $( '#section' ).click(function(event){
  	event.stopPropagation();
  	$( '.button' ).toggleClass('open');
  });
  
  // Function click out and close function up
  $( document ).click( function() {
		var btn = $( '.button' );
		if(btn.hasClass( 'open' )) {
			btn.removeClass( 'open' );
		}
	});
});