gamepad_demo.js

var gamepad = null;
var timer = null;

window.addEventListener("gamepadconnected", function(e) {
  if (!gamepad) {
    gamepad = e.gamepad;
    timer = setInterval('updateStatus()', 100);
  }
});

window.addEventListener("gamepaddisconnected", function(e) {
  gamepad = null;
  clearInterval(timer);
});

function updateStatus() {
  if (gamepad) {
    var status = {
      buttons: [],
      axes: []
    };

    for (var i = 0; i < gamepad.buttons.length; i++) {
      var button = gamepad.buttons[i];
      var pressed = (button.pressed || button.value > 0);
      status.buttons.push(pressed);
    }

    for (var i = 0; i < gamepad.axes.length; i++) {
      var axes = gamepad.axes[i];
      status.axes.push(axes.toFixed(4));
    }

    showStatus(status);
  }
}

function showStatus(status) {
  for (var i = 0; i < status.buttons.length; i++) {
    var button = status.buttons[i];
    if (button) {
      console.log('button' + i + ' pressed');
    }
  }

  for (var i = 0; i < status.axes.length; i++) {
    var axes = status.axes[i];
    console.log('axes' + i + ': ' + axes);
  }
}