LeCodesdocs

QRScanner

The host's native full-screen QR scanner. Host-optional: the le.codes app provides it, the generic web viewer (and other hosts) don't — always guard with QRScanner.isSupported before offering the feature.

At a glance

TypeScript
if (QRScanner.isSupported) {
  const scanner = new QRScanner(data => {
    if (data === null) return          // a camera frame with no readable code
    console.log('scanned:', data)
    scanner.close()
  })
  await scanner.open()                 // asks for camera permission, then opens the scanner
}

API

TypeScript
QRScanner.isSupported: boolean                        // static — does this host have a scanner?

new QRScanner(onData: (data: string | null) => void)  // onData fires per decoded frame
scanner.open(): Promise<void>                         // request camera access, open the scanner
scanner.close(): void                                 // close the scanner, release the camera
  • onData fires for every value the scanner decodes; null means a frame with no readable code, so expect it repeatedly while the user is aiming. The same code can be reported more than once — debounce/close() yourself when you've got what you need.
  • open() runs two steps in order: request camera permission, then open the native scanner. The promise resolves once the scanner is open and rejects if the user denies camera access.
Note

unlike physics (which silently no-ops when absent), open() throws an Error on hosts without a scanner. isSupported is the guard — check it before showing a "Scan" button at all. See host gating.

Note

lifecycle — the scanner holds the camera until close() is called. If you open it from a screen, close it in the screen's onClose (and after a successful scan) or the camera stays captured.

See also

← BackCameraViewer