$.fn.selectRange = function(start, end) {

    if(typeof end === 'undefined') {

        end = start;

    }

    return this.each(function() {

        if('selectionStart' in this) {

            this.selectionStart = start;

            this.selectionEnd = end;

        } else if(this.setSelectionRange) {

            this.setSelectionRange(start, end);

        } else if(this.createTextRange) {

            var range = this.createTextRange();

            range.collapse(true);

            range.moveEnd('character', end);

            range.moveStart('character', start);

            range.select();

        }

    });

};

​

​

var toggle = false;

​

setInterval(function() {

    if(toggle) {

        $('#hw').selectRange(6, 15);

    } else {

        $('#hw').selectRange(8);

    }

    toggle = !toggle;

}, 500);

​

$('#focus').on('click', function() {

  $('#hw').focus();

});