<script>
<input type="button" value="button" id="target"
onclick="alert('Hello World ' + document.getElementById('target').value)">
</script>
<script>
<input type="button" value="button2" id="target2"
onclick="alert('Hello World ' + this.value)">
</script>
<script>
let t = document.getElementById("btn");
t.onclick = function (event) {
// alert("Hello world" + event.target.value);
console.dir(event);
}
</script>
<script>
let t = document.getElementById("target");
t.addEventListener('click',function(event){
alert("Hello Wolrd " + event.target.value);
});
</script>