JSFiddle - React, Tailwind, and code Playground

HTML

<div id="start" style="display: none;">
    <span>1</span>
    <div>
        <span>1.1</span>
        <div>
            <span>1.1.1</span>
            <span>1.1.2</span>
        </div>
    </div>
    <div>
        <span>1.2</span>
    </div>
    <div>
        <span>1.3</span>
        <div>
            <span>1.3.1</span>
            <span>1.3.2</span>
        </div>
    </div>
</div>

<textarea rows="20"></textarea>

JavaScript

$(function () {
    var x = $('#start').find('div');
    x.each(function () {
        $('>span', this).each(function () {
            $('textarea').append($(this).text() + '\n');
        });
    });
});