how to use onclick event code example

Example 1: javascript onclick

document.getElementById("myBtn").addEventListener("click", function() {
  alert("Hello World!");
});

Example 2: onclick="to Function()

<button onclick="topFunction()" id="myBtn" title="Go to top">Top</button>


<script>
//Get the button
var mybutton = document.getElementById("myBtn");

// When the user scrolls down 20px from the top of the document, show the button
window.onscroll = function() {scrollFunction()};

function scrollFunction() {
  if (document.body.scrollTop > 20 || document.documentElement.scrollTop > 20) {
    mybutton.style.display = "block";
  } else {
    mybutton.style.display = "none";
  }
}

// When the user clicks on the button, scroll to the top of the document
function topFunction() {
  document.body.scrollTop = 0;
  document.documentElement.scrollTop = 0;
}
</script>

Example 3: onclick in js

<input type="text" name="text" id="test" onmouseover="skriv('klick')">
    <input type="button" name="send" value="Skicka" id="klick" onclick="skriv('test')">
    
    
    <script src="lib/script.js"></script>


// in lib/script.js

  function skriv(name) {
    document.getElementById(name).style.backgroundColor='red';
  }