Filtro elementi

 <!-- Control buttons -->
<div id="myBtnContainer">
 <button class="btn active" onclick="filterSelection('all')"> Mostra tutti</button>
 <button class="btn" onclick="filterSelection('macchine')"> Macchine</button>
 <button class="btn" onclick="filterSelection('animali')"> Animali</button>
 <button class="btn" onclick="filterSelection('frutti')"> Frutti</button>
 <button class="btn" onclick="filterSelection('colori')"> Colori</button>
</div>


<!-- The filterable elements. Note that some have multiple class names (this can be used if they belong to multiple categories) -->
<div class="container">
 <div class="filterDiv macchine">BMW</div>
 <div class="filterDiv frutti">Arancia</div>
 <div class="filterDiv macchine">Volvo</div>
 <div class="filterDiv colori">Rosso</div>
 <div class="filterDiv animali">Cavallo</div>
 <div class="filterDiv macchine">Audi</div>
 <div class="filterDiv colori">Blu</div>
 <div class="filterDiv animali">Gatto</div>
 <div class="filterDiv animali">Cane</div>
 <div class="filterDiv frutti">Melone</div>
 <div class="filterDiv frutti">Kiwi</div>
 <div class="filterDiv frutti">Banana</div>
 <div class="filterDiv frutti">Limone</div>
 <div class="filterDiv animali">Tigre</div>
 <div class="filterDiv colori">Arancione</div>
 <div class="filterDiv colori">Giallo</div>

</div>

.container {
 overflow: hidden;
}


.filterDiv {
 float: left;
 background-color: #2196F3;
 color: #ffffff;
 width: 100px;
 line-height: 100px;
 text-align: center;
 margin: 2px;
 display: none; /* Hidden by default */
}

/* The "show" class is added to the filtered elements */
.show {
 display: block;
}

/* Style the buttons */
.btn {
 border: none;
 outline: none;
 padding: 12px 16px;
 background-color: #f1f1f1;
 cursor: pointer;
}

/* Add a light grey background on mouse-over */
.btn:hover {
 background-color: #ddd;
}

/* Add a dark background to the active button */
.btn.active {
 background-color: #666;
 color: white;
}

<script>
 filterSelection("all")
function filterSelection(c) {
 var x, i;
 x = document.getElementsByClassName("filterDiv");
 if (c == "all") c = "";
 // Add the "show" class (display:block) to the filtered elements, and remove the "show" class from the elements that are not selected
 for (i = 0; i < x.length; i++) {
 w3RemoveClass(x[i], "show");
 if (x[i].className.indexOf(c) > -1) w3AddClass(x[i], "show");
 }
}


// Show filtered elements
function w3AddClass(element, name) {
 var i, arr1, arr2;
 arr1 = element.className.split(" ");
 arr2 = name.split(" ");
 for (i = 0; i < arr2.length; i++) {
 if (arr1.indexOf(arr2[i]) == -1) {
 element.className += " " + arr2[i];
 }
 }
}

// Hide elements that are not selected
function w3RemoveClass(element, name) {
 var i, arr1, arr2;
 arr1 = element.className.split(" ");
 arr2 = name.split(" ");
 for (i = 0; i < arr2.length; i++) {
 while (arr1.indexOf(arr2[i]) > -1) {
 arr1.splice(arr1.indexOf(arr2[i]), 1);
 }
 }
 element.className = arr1.join(" ");
}

// Add active class to the current control button (highlight it)
var btnContainer = document.getElementById("myBtnContainer");
var btns = btnContainer.getElementsByClassName("btn");
for (var i = 0; i < btns.length; i++) {
 btns[i].addEventListener("click", function() {
 var current = document.getElementsByClassName("active");
 current[0].className = current[0].className.replace(" active", "");
 this.className += " active";
 });
}
</script>