Menu should close when click on the link

<button id="showLeft">Show/Hide Left Slide Menu</button>

        <nav class="cbp-spmenu cbp-spmenu-vertical cbp-spmenu-left" id="cbp-spmenu-s1">
            <ul>
                <li><a href="#">Celery seakale</a></li>
                <li><a href="#">Dulse daikon</a></li>
                <li><a href="#">Zucchini garlic</a></li>
                <li><a href="#">Catsear azuki bean</a></li>
                <li><a href="#">Dandelion bunya</a></li>
                <li><a href="#">Rutabaga</a></li>
    </ul>
            </nav>

var menuLeft = document.getElementById( 'cbp-spmenu-s1' ),
                    body = document.body;

                showLeft.onclick = function() {
                    classie.toggle( this, 'active' );
                    classie.toggle( menuLeft, 'cbp-spmenu-open' );

                };