Clear cart on browser close(sessionStorage, AJAX)

<script>

var readValue = sessionStorage['myvariable'];
if(readValue){
}else{
$.ajax({
type: "POST",
url: '/cart/clear.js',
success: function(){
console.log('clear');
$('.cart-count').addClass('hidden-count');
},
dataType: 'json'
});
}

var myVariable = "Session";

sessionStorage['myvariable'] = myVariable;
console.log(readValue);
</script>