cross-browser input text selection and selected range

inputCaret.js

/**
* input = DOM or jquery object
* [begin] = Number
* [end] = Number
* If begin and end are not specified, returns the current input selection
**/
var inputCaret = function(input, begin, end) {
  var npt = input.jquery && input.length > 0 ? input[0] : input, range;
  if (typeof begin == 'number') {
    if (!$(input).is(':visible')) {
      return;
    }
    end = (typeof end == 'number') ? end : begin;
    if (npt.setSelectionRange) {
      npt.selectionStart = begin;
      npt.selectionEnd = end;

    } else if (npt.createTextRange) {
      range = npt.createTextRange();
      range.collapse(true);
      range.moveEnd('character', end);
      range.moveStart('character', begin);
      range.select();
    }
  } else {
    if (!$(input).is(':visible')) {
      return { "begin": 0, "end": 0 };
    }
    if (npt.setSelectionRange) {
      begin = npt.selectionStart;
      end = npt.selectionEnd;
    } else if (document.selection && document.selection.createRange) {
      range = document.selection.createRange();
      begin = 0 - range.duplicate().moveStart('character', -100000);
      end = begin + range.text.length;
    }
    return { "begin": begin, "end": end };
  }
};