const keepLastIndex = (obj)=> {
if (window.getSelection) { //ie11 10 9 ff safari
obj.focus(); //解决ff不获取焦点无法定位问题
const range = window.getSelection(); //创建range
range.selectAllChildren(obj); //range 选择obj下所有子内容
range.collapseToEnd(); //光标移至最后
} else if (document.selection) { //ie10 9 8 7 6 5
const range = document.selection.createRange(); //创建选择对象
//var range = document.body.createTextRange();
range.moveToElementText(obj); //range定位到obj
range.collapse(false); //光标移至最后
range.select();
}
}