Make an action on class or id affect other - html

Question

I am working with a Web Form (html) and a CSS file and I wanna know what do I need to write in the CSS to make an action on one class or id- affect an other class or id. For example: I have a
<p class="hh">
Hello!
</p>
(^^ this p tag's class is "hh")
And another one:
<p class="gb">
Goodbye!
</p>
(^^ this p tag's class is "gb")
I wanna write something in the CSS file so that whenever I click on whatever there is in the "hh" class, it will make something change in the "gb" class, so if I click on the text "Hello!" it will make the color of the text "Goodbye!" green. Please help me! I try to find out how to do it for a long long time...
Thank you!

Answer 1

This sounds more like you need a javascript solution. In general you are not really able to change something on a click event in CSS. Consider following solution:
const hh = document.getElementById("hh");
const gb = document.getElementById("gb");
hh.addEventListener("click", function() {
gb.style.color = "green";
});
gb.addEventListener("click", function() {
hh.style.color = "red";
});
<div id="hh">
Hello!
</div>
<div id="gb">
Goodbye!
</div>

Answer 2

A common practice for doing this is by using JavaScript, which is known as the programming language of the web. If you've never used JavaScript before it can be a little bit confusing but if you have experience in other general purpose programming languages such as Python or Java then it shouldn't take much time to pick up.
To do what you are asking, there are a few possible ways to do this. I will share what I believe to be the most simple although not the most robust. You can use JavaScript events to fire off certain functions when certain particular things happen to your elements. For example, you can modify your HTML like so:
<p class="hh" onclick="doSomething()">Hello!</p>
Then, either in a separate JavaScript file linked back to your html file or in the of your html file, you would define the doSomething() function:
function doSomething(){
document.getElementsByClassName("gb")...
}
The document.getElementsByClassName() function is one way to select HTML elements from a page and modify it via JavaScript, I suggest checking out the very good JavaScript tutorials on W3Schools for more and better ways to do this, but this is the general principal. You would then modify the HTML element any way you need to.
Hope this helps!

Answer 3

You need to do that using JavaScript. I have attached a example for that.
$(".one").on('click', function() {
$(".two").css('color', 'red');
})
.one{
cursor: pointer;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<p class="one"> Change below text to RED </p>
<p class="two"> Black text </p>

Answer 4

There is a way to use a :focus state to change the look of parents, but it wouldn't be possible to differentiate between which click caused the parent to focus.
Here's a simple example using JavaScript and jQuery.
var helloEls = document.querySelectorAll('#jsTest .hh');
var goodbyeEls = document.querySelectorAll('#jsTest .gb');
helloEls.forEach(function(elem) {
elem.addEventListener("click", function() {
goodbyeEls.forEach(function(el) {
if (el.className==='gb active'){
el.className = 'gb';
} else {
el.className = 'gb active';
}
});
});
});
var gbEls = $('#jqueryTest .gb');
$('#jqueryTest .hh').click(function(){
if (gbEls.hasClass('active')){
gbEls.removeClass('active');
} else {
gbEls.addClass('active');
}
});
.gb.active {
color: green;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="jsTest">
<p class="hh">
Hello!
</p>
<p class="gb">
Goodbye!
</p>
</div>
<div id="jqueryTest">
<p class="hh">
Hello!
</p>
<p class="gb">
Goodbye!
</p>
</div>