Trying toggle method to introduce new class on button click - html

Question

I am trying to introduce new class for specific div element using nth-child() pseudo-class but it is not working!
Am I doing something wrong?
Note that menu, container, newClass are already defined in CSS section and I'm not showing them here.
Here is what I am trying:
$(function() {
$("button").click(function {
$("div:nth-child(2)").toggleClass("newClass");
});
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<button>Toggle CSS</button>
<div class="container">
<div class="menu">
<lu>
<li>option 1</li>
<li>option2</li>
<li>option 3</li>
</lu>
</div>
</div>

Answer 1

There are lots of mistakes in your code. Which div are you want to add a class newClass? I think your code should be like this
$(function() {
$("button").on('click', function() {
$(".menu").toggleClass("newClass");
});
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<button>Toggle CSS</button>
<div class="container">
<div class="menu">
<ul>
<li>option 1</li>
<li>option2</li>
<li>option 3</li>
</ul>
</div>
</div>

Answer 2

My mistake
I should not use
<script>
$("div:nth-child(2)").toggle Class("newClass");
</script>
this to introduce new class for div element, with the class menu , as it is not a second child of div . What given below is though working fine for me:
Correction
<script>
$("div.menu").toggleClass("newClass");
</script>
That is: to specify div element(whose class is going to be toggled) by tagging its class menu , to call jQuery for div with the class menu .
Also by mistake parentheses () were missing.