textarea 光标位置获取

_getFocus(elem) {  //光标位置-获取
				var s,e,range,stored_range;
		        if(elem.selectionStart == undefined){//ie
		            var selection=document.selection;
		            if (elem.tagName.toLowerCase() != "textarea") {
		                var val = $(elem).val();
		                range = selection.createRange().duplicate();
		                range.moveEnd("character", val.length);
		                s = (range.text == "" ? val.length:val.lastIndexOf(range.text));
		                range = selection.createRange().duplicate();
		                range.moveStart("character", -val.length);
		                e = range.text.length;
		            }else {//textarea
		                range = selection.createRange(),
		                stored_range = range.duplicate();
		                stored_range.moveToElementText(elem);
		                stored_range.setEndPoint('EndToEnd', range);
		                s = stored_range.text.length - range.text.length;
		                e = s + range.text.length;
		            }
		        }else{//chrome  fire
		            s=elem.selectionStart,
		            e=elem.selectionEnd;
		        }
		       var te=elem.value.substring(s,e);
		       return s
			},_getFocus(elem) {  //光标位置-获取
				var s,e,range,