javascript - How to get the number of the parent element of a future element among all the same elements on the page?

Question

The entire code is dynamically added to the page through js. When b changes, how to get the position (position) of a among all a's on the page?

<p class="a">
    <p class="b"></p>
</p>

Answer 1

I don’t quite understand what it means

If the class name of a is unchanged, use jQuery directly

$(".a").index(this.parent())

where this is the changed b

Answer 2

[...document.querySelector('.b').parentNode.parentNode.children].indexOf(document.querySelector('.b').parentNode)

Answer 3

Since it is added dynamically, why not give it an identifier before adding it to the dom? For example:

<p class="a" index="1">
    <p class="b"></p>
</p>
<p class="a" index="2">
    <p class="b"></p>
</p>
...

In this way, when b changes, just get the parent’s index attribute directly