if you're using the standard Android Browser, you can't control DataWedge behaviour from your web page: DataWedge is the Zebra service that allows to integrate barcode scanning into your native/web application without having to write any code. Writing a native app you can have some integration with DataWedge, but this is not an option for web application. Here's DataWedge guide.
What you can do on a standard web app is to intercept the keypress event and drive the data coming from DataWedge into the correct input field. However, Android v4.4 includes a bug in the webview component that affect this functionality:
If you want to have full control of the device scanner (and more) you can use Zebra Technologies' Enterprise Browser that include APIs to control the scanner behaviour. You can find more information here.