取得焦点位置

function getCursorPos(obj){
?var CaretPos=0;
?var $IE = navigator.userAgent.indexOf('MSIE')!=-1;
?if($IE){
??var ds=document.selection;
??obj.focus();
??var range=null;
??range=ds.createRange();
??
??var stored_range=range.duplicate();
??
??stored_range.moveToElementText(obj);
??stored_range.setEndPoint("EndToEnd",range);
??obj.selectionStart=stored_range.text.length-range.text.length;
??obj.selectionEnd=obj.selectionStart+range.text.length;
??CaretPos=obj.selectionStart
??}else{
??if(obj.selectionStart||obj.selectionStart=="0")
??{
???CaretPos=obj.selectionStart;
??}
??}
??return CaretPos
?};