function keepLastIndex(obj) {
    if (window.getSelection) {//ie11 10 9 ff safari
        obj.focus(); //解決ff不獲取焦點(diǎn)無法定位問題
        var range = window.getSelection();//創(chuàng)建range
        range.selectAllChildren(obj);//range 選擇obj下所有子內(nèi)容
        range.collapseToEnd();//光標(biāo)移至最后
    }
    else if (document.selection) {//ie10 9 8 7 6 5
        var range = document.selection.createRange();//創(chuàng)建選擇對象
        //var range = document.body.createTextRange();
        range.moveToElementText(obj);//range定位到obj
        range.collapse(false);//光標(biāo)移至最后
        range.select();
    }
}