example.jade

html
  head
    title Socket.io Example
  body
    h1(class="something") Socket.io Example

    input#msg(type="text")
    button send message
    #messages

    script(src="/socket.io/socket.io.js")
    script(src="//ajax.googleapis.com/ajax/libs/jquery/3.1.0/jquery.min.js")
    script.
      var socket = io();

      $('button').on('click', function() {
        socket.emit('message', $('#msg').val());
      });

      socket.on('message', function(msg) {
        var $span = $('<div>');
        $span.text(msg);
        $('#messages').append($span);
      });