原div
<div id='div'>
<p>
123456
<br>
abc
<br>
</p>
</div>
```
要求:在a后面插入字符串xxxf,怎样是光标定位到xxxf后面
实现逻辑
const div = document.getElementById('div')
div.innerHTML = '
123456
abxxxfc
const range = document.createRange()
range.setStart(div.children[0], 13) // 13是f的位置
执行报错
IndexSizeError: Failed to execute 'setStart' on 'Range': There is no child at offset 13.