addeventlistener javascript fucntion code example

Example 1: javascript onclick event listener

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

Example 2: addeventlistener js to change style

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

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

    if (curColour === 'red') {
        document.body.style.backgroundColor = "blue";
    }
    else {
        document.body.style.backgroundColor = "red";
    }
});