javascript - Can't get JS to run

I found a slider menu on CodePen I liked but no matter what I do I can't get the JS to run. I actually tried multiple sources of code and none worked properly.

    
    

    



    

    

    

  
  

    


      

        

          Home
        
        

           Hike
        
        

          Bike
        

        

          Fishing
        
        

          Run
          

        

          Triple Crown
          

        


          Gallery
        

          Contact
        
      
    
  
  

CSS:

html {
  height: 100%; 
}

body {
  height: 100%;

  margin: 0;
  padding: .1px;
  position: relative;
  background: url(http://www.adventuresofscatman.com/wp-content/uploads/2015/09/IMG_4273.jpg);
  background-size: cover;
  overflow-x: hidden;
}

.button{
  position: absolute;

  top: 30px;
  left: 25px;;
  width: 55px;
  height: 50px;
}

.button div {
  height: 20%;
  border-top: 7px solid rgb(103, 103, 103);
  cursor: pointer;

  transition: .5s;
}

.button:hover div {
  border-color: rgb(139, 139, 139); 
}

.menu-in,
.menu-out {
  padding: .1px;

  width: 240px;
  height: 100%;
  background: rgba(0, 0, 0, .65);
  overflow: hidden;
  position: absolute;
  top: 0;
}

.menu-in {
  -webkit-animation: menu-in .9s forwards ease;

}

.menu-out{
  -webkit-animation: menu-out .4s forwards ease-in; 
}

ul {
  margin: 68px 0 0 0;
  padding: 0;
}


.menu-item {
  list-style: none;
}

.link {
  display: block;
  text-decoration: none;
  color: rgb(190, 190, 190);
  font: 28px/50px arial;

  text-transform: uppercase;
  height: 50px;
  text-align: center;
  transition: .1s;
}

.link:hover {
  color: rgb(230, 230, 230);
  background: rgba(200, 200, 200, .1); 
}


.shadow-in,
.shadow-out{
  width: 100%;
  height: 100%;
  position: absolute;
  top: 0;
  background: rgba(0, 0, 0, .4);
}


.shadow-in {
  -webkit-animation: shadow-in .9s forwards ease;
}

.shadow-out {
   -webkit-animation: shadow-out .4s forwards ease-in;
}

.none {
  display: none;

}

@-webkit-keyframes menu-in {
  0% {
    left: -240px;
  }
  100% {
    left: 0;
  }
}


@-webkit-keyframes menu-out {
  0% {
    left: 0;
  }
  100% {
    left: -240px;
  }
}  


@-webkit-keyframes shadow-in {
  0% {
    left: 0;
    opacity: 0;
  }
  100% {
    left: 240px;
    opacity: 1;
  }
}


@-webkit-keyframes shadow-out {
  0% {
    left: 240px;
    opacity: 1;
  }
  99%{
    height: 100%; 
  }
  100% {

    height: 0;
    left: 0;
    opacity: 0;
  }
}

JS:

document.getElementById('button').addEventListener('click', function() {

    showMenu();
});

document.getElementById('menu').addEventListener('click', function() {
    showMenu();
});

function showMenu() {
    console.log('click');
    var menu = document.getElementById('menu');

    var shadow = document.getElementById('shadow');
    var button = document.getElementById('button');

    menu.className = 'menu-in';
    shadow.className = 'shadow-in';
    button.className = 'none';
}

document.getElementById('shadow').addEventListener('click', function() {
    var menu = document.getElementById('menu');

    var shadow = document.getElementById('shadow');
    var button = document.getElementById('button');

    menu.className = 'menu-out';
    shadow.className = 'shadow-out';
    button.className = 'button';
});