<body>
<p class="demo">JavaScript can change the content of an HTML element.</p>
<p class="demo">Yolo</p>
<button type="button" onclick="myFunction()">Click Me!</button>
<script>
function myFunction()
{
x=document.getElementsByClassName("demo"); // Find the elements
for(var i = 0; i < x.length; i++){
x[i].innerText="Hello JavaScript!"; // Change the content
}
}
</script>
</body>