51.js

// An event is an important part of JavaScript.A web page respond according to an event occurred. Some events are user generated and some are generated by API’s. An event listener is a procedure in JavaScript that waits for an event to occur. The simple example of an event is a user clicking the mouse or pressing a key on the keyboard.
//Example when I press subscribe,youtube subscribes me to the youtube channel


function hide() {
    let para = document.getElementById('para');
    let btn = document.getElementById('btn');
    console.log(para.style.display);
    if (para.style.display != 'none') {
        para.style.display = 'none';
    }
    else {
        para.style.display = 'block';
    }
}

let para = document.getElementById('para');
        para.addEventListener('mouseover', function run(){
            alert('Mouse Inside');
            console.log('Mouse Inside');
        });
        para.addEventListener('mouseout', function run(){
            alert('Mouse Outside');
            console.log('Mouse Outside');
        });