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

I wrote this answer, because my Barcode Scanner Motorola LS1203 generated keypress event, so I can’t use Utkanos’s solution.

My solution is:

var BarcodeScanerEvents = function() {
     this.initialize.apply(this, arguments);
};

BarcodeScanerEvents.prototype = {
    initialize: function() {
       $(document).on({
          keyup: $.proxy(this._keyup, this)
       });
    },
    _timeoutHandler: 0,
    _inputString: '',
    _keyup: function (e) {
        if (this._timeoutHandler) {
            clearTimeout(this._timeoutHandler);
            this._inputString += String.fromCharCode(e.which);
        } 

        this._timeoutHandler = setTimeout($.proxy(function () {
            if (this._inputString.length <= 3) {
                this._inputString = '';
                return;
            }

            $(document).trigger('onbarcodescaned', this._inputString);

            this._inputString = '';

        }, this), 20);
    }
};