how to change color when when click button javascript code example

Example 1: change background color on button click in javascript

<style>
  .bg1 {
  	background-color: red;
  }
</style>

<button id="btnChangebgColor" />

<script>
  	$(document).ready(function(){
      $("#btnChangebgColor").click(function() {
        $(this).addClass(".bg1");
      }); 
	}
</script>

Example 2: change color by click event javascript

var button = document.querySelector("button");

button.addEventListener("click", function() {
    const curColour = document.body.style.backgroundColor;

    document.body.style.backgroundColor = curColour === 'red' ? 'blue' : 'red';
});