我相信下面的JS代码应该适合你：

// Get all serial ports the user has previously granted the website access to.
const ports = await navigator.serial.getPorts();

来源：https://web.dev/serial/#open-port

在第一个鼠标或键盘事件上运行此代码，它将在第一次运行时弹出端口权限，并在下次运行时自动获取端口。

// specify device details
let usbVendorId = 0x0403, // Arduino
    usbProductId = 0x6001; // Nano

// get serial ports
navigator.serial
.getPorts()
.then(
    ports => {

        // no ports available, prompt user permission
        if(!ports.length) 
            return navigator.serial
            .requestPort({
                filters: [{usbVendorId, usbProductId}]
            });
        // port is available
        else 
            return Promise
            .resolve(ports[0]);

    }
)
.then(
    port => {

        port
        .open({
            baudRate: 9600
        })
        .then(
            () => {

                const reader = port.readable.getReader();

                // ...

            }
        );

    }
);