JSFiddle - React, Tailwind, and code Playground

HTML

<input type="checkbox" id="set_1" checked> click to show text1
<p class = "wpbook_hidden wpbook_option_set_1"> This is option one</p>
<p class = "wpbook_hidden wpbook_option_set_1"> This is another option one</p>
<input type="checkbox" id="set_2"> click to show text1
<p class = "wpbook_hidden wpbook_option_set_2"> This is option two</p>

JavaScript

$('.wpbook_hidden').css({
    'display': 'none'
});

alert($('#set_1')[0].checked)
$(':checkbox').change(function() {
    var option = 'wpbook_option_' + $(this).attr('id');
    if ($('.' + option).css('display') == 'none') {
        $('.' + option).fadeIn();
    }
    else {
        $('.' + option).fadeOut();
    }
});