Detect when input box filled by keyboard and when by barcode scanner.

Question

How I can programmatically detect when text input filled by typing on keyboard and when it filled automatically by bar-code scanner?

Answer 1

For ES6 2019 version of Vitall answer.

const events = mitt()

class BarcodeScaner {
  initialize = () => {
    document.addEventListener('keypress', this.keyup)
    if (this.timeoutHandler) {
      clearTimeout(this.timeoutHandler)
    }
    this.timeoutHandler = setTimeout(() => {
      this.inputString = ''
    }, 10)
  }

  close = () => {
    document.removeEventListener('keypress', this.keyup)
  }

  timeoutHandler = 0

  inputString = ''

  keyup = (e) => {
    if (this.timeoutHandler) {
      clearTimeout(this.timeoutHandler)
      this.inputString += String.fromCharCode(e.keyCode)
    }

    this.timeoutHandler = setTimeout(() => {
      if (this.inputString.length <= 3) {
        this.inputString = ''
        return
      }
      events.emit('onbarcodescaned', this.inputString)

      this.inputString = ''
    }, 10)
  }
}

Can be used with react hooks like so:

const ScanComponent = (props) => {
  const [scanned, setScanned] = useState('')
  useEffect(() => {
    const barcode = new BarcodeScaner()
    barcode.initialize()
    return () => {
      barcode.close()
    }
  }, [])

  useEffect(() => {
    const scanHandler = code => {
      console.log(code)
      setScanned(code)
    }

    events.on('onbarcodescaned', scanHandler)
    return () => {
      events.off('onbarcodescaned', scanHandler)
    }
  }, [/* here put dependencies for your scanHandler ;) */])
  return 
{scanned}
}

I use mitt from npm for events, but you can use whatever you prefer ;)

Tested on Zebra DS4208