gamepad.js

var emulatedGamepad = {
    id: "Emulated iOS Controller",
    index: 0,
    connected: true,
    timestamp: 0,
    mapping: "standard",
    axes: [0, 0, 0, 0],
    buttons: new Array(17).fill().map(m => ({pressed: false, touched: false, value: 0}))
}

navigator.getGamepads = function() {

    window.webkit.messageHandlers.controller.postMessage({}).then((controllerData) => {

        try {

            var data = JSON.parse(controllerData);

            for(let i = 0; i < data.buttons.length; i++) {
                
                emulatedGamepad.buttons[i].pressed = data.buttons[i].pressed;
                emulatedGamepad.buttons[i].value = data.buttons[i].value;
            }

            for(let i = 0; i < data.axes.length; i++) {
                
                emulatedGamepad.axes[i] = data.axes[i]
            }

        } catch(e) {

        }
    });

    return [emulatedGamepad, null, null, null];
};