text: var http = require('http');
  
  const page = {
      props: [
          {
              name: 'counter',
              value: 1
          }
      ],
      blocks: [
          {
              type: 'button',
              value: 'カウンター ${prop("counter")}',
              attrs: {
                  onClick: {
                      action: 'updateProps',
                      payload: {
                          props: [
                              {
                                  name: 'counter',
                                  newValue: '${add(prop("counter"), 1)}'
                              }
                          ]
                      }
                  }
              }
          }
      ]
  };
  
  var app = http.createServer(function (req, res) {
      // Enable CORS, so that clients can call the Hook.
      res.setHeader('Access-Control-Allow-Origin', '*')
      res.setHeader('Access-Control-Allow-Methods', 'GET, POST, DELETE, OPTIONS')
      res.setHeader('Access-Control-Allow-Headers',
          'Authorization, Accept, Content-Type')
  
      res.writeHead(200, {'Content-Type': 'application/json'});
      res.end(JSON.stringify(page));
  })
  
  app.listen(process.argv[2] || 3000);
  