Disable keyboard with HTML input and allow scanners

Question

I have an HTML input

<input type="text" id="txtInput">

and I need to disable all keyboard keys for input, only to allow barcode scanners to get the data of the barcode and fill it with the input.

I tried "readonly" and "disabled" and javaScript keydown, but all those solutions disable everything including barcode scanners too.

Is there's any way for doing this?

Answer 1

So first you need to understand that barcode scanners pretend to be keyboards. So they will trigger JS keystroke events just like real keyboards. The only way I can think of to separate the 2 is some timing-based heuristic (the idea being that nobody can type an entire 10-digit barcode in less than 0.1 seconds).

So basically, you would have some javascript that would do something along these lines:

• (onkeydown) append the pressed key to a global string and start a timer with setTimeout (with very low delay, say 10 ms)
• (onkeydown) append the pressed key as before, but don't start the timer again
• in your setTimeout function, check if the string of keypresses is at least 3 keys (or longer, depending on the barcodes that you expect). If so, write the string to the input field. Otherwise, drop the string
• rinse and repeat

It's gonna be ugly, but if you're really desperate, it might work

var delay = (function(){
   var timer = 0;
   return function(callback, ms){
      clearTimeout (timer);
      timer = setTimeout(callback, ms);
   };
})();

$("#txtInput").on("input", function() {
   delay(function(){
      if ($("#txtInput").val().length < 8) {
          $("#txtInput").val("");
      }
   }, 20 );
});