USBDevice: opened property
Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.
The opened
read only property of the
USBDevice
interface indicates whether a session has been started with a
paired USB device. A device must be opened before it can be controlled by a web page.
Value
A boolean
.
Examples
This example is for a hypothetical USB device with a multi-colored LED. It shows how to
test that a device is open before calling USBDevice.controlTransferOut
to
set a specified LED color.
Note: What data can be passed to a USB device and how it is passed is particular and unique to each device.
js
async function setDeviceColor(usbDevice, r, g, b) {
if (device.opened) {
// This hypothetical USB device requires that the data passed to
// it be in a Uint8Array.
const payload = new Uint8Array([r, g, b]);
await usbDevice.controlTransferOut(
{
requestType: "vendor",
recipient: "device",
request: 1,
value: 0,
index: 0,
},
payload
);
}
}
Specifications
Specification |
---|
WebUSB API # ref-for-dom-usbdevice-opened |
Browser compatibility
BCD tables only load in the browser