If you want to add class in click li and remove all other class from all li then you can use simple jQuery code. Sometime we need to set active class for menu or other in this case this code is very helpful. This is simple code which set new class and remove all class from li.

        $('.list li').click(function() {
             $( '.list li' ).removeClass( "active" ); // remove active class from all li 
            $(this).addClass('active'); // add active class for click li

then this is html code

active {
   li {
   cursor: pointer;

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<ul class="list">
            <li>Test 1</li>
            <li>Test 2</li>
            <li>Test 3</li>
            <li>Test 4</li>
            <li>Test 5</li>
            <li>Test 6 </li>
            <li>Test 7</li>

When you click any li then remove all class and add active class , i also add a css which color is red then easily can understand it.
If you face any problem then please inform me. I will try to help you.