function fn caret function pos var target this if arguments length get

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(function($) {
$.fn.caret = function(pos) {
var target = this[0];
if (arguments.length == 0) { //get
if (target.selectionStart) { //DOM
var pos = target.selectionStart;
return pos > 0 ? pos : 0;
}
else if (target.createTextRange) { //IE
target.focus();
var range = document.selection.createRange();
if (range == null)
return '0';
var re = target.createTextRange();
var rc = re.duplicate();
re.moveToBookmark(range.getBookmark());
rc.setEndPoint('EndToStart', re);
return rc.text.length;
}
else return 0;
} //set
if (target.setSelectionRange) //DOM
target.setSelectionRange(pos, pos);
else if (target.createTextRange) { //IE
var range = target.createTextRange();
range.collapse(true);
range.moveEnd('character', pos);
range.moveStart('character', pos);
range.select();
}
}
})(jQuery)