Introduction

The goal of this tutorial is to familiarize you with the fundamental aspects of Javascript events. You will learn how events are used to trigger specific functionalities, adding interactivity to your web applications.

By the end of this tutorial, you will understand:
1. How to trigger Javascript events
2. How to handle events using event handlers
3. How to use event listeners

Prerequisite: Basic understanding of HTML and Javascript syntax.

Step-by-Step Guide

An event in Javascript is an action that can be detected by our Javascript code. Common examples include a mouse click, a key press, or a page load.

Event Handlers

Event handlers are javascript functions that are triggered when a specific event occurs. For example, if you want to run a function when a button is clicked, you would use the onclick event handler.

// HTML code
<button id="myButton">Click me!</button>

// Javascript code
document.getElementById("myButton").onclick = function() {
    alert("You clicked the button!");
};

In the above example, when the button with id "myButton" is clicked, an alert box pops up with the message "You clicked the button!".

Event Listeners

Event listeners are similar to event handlers, but they offer more flexibility. For example, they can handle multiple events for the same element.

// HTML code
<button id="myButton">Click me!</button>

// Javascript code
document.getElementById("myButton").addEventListener("click", function() {
    alert("You clicked the button!");
});

In this example, an event listener is added to the button. When the button is clicked, it triggers the same alert as before.

Code Examples

Here are some more practical examples of Javascript events.

Mouseover Event

This event is triggered when the mouse pointer is moved onto an element.

<!-- HTML code -->
<div id="myDiv">Hover over me!</div>

<!-- JavaScript code -->
document.getElementById("myDiv").addEventListener("mouseover", function() {
    this.style.backgroundColor = "red";
});

In the above code, when you hover over the div, the background color changes to red.

Keydown Event

This event is triggered when a key is pressed down.

<!-- HTML code -->
<input id="myInput" type="text">

<!-- JavaScript code -->
document.getElementById("myInput").addEventListener("keydown", function(event) {
    console.log("Key pressed: " + event.key);
});

In this example, whenever a key is pressed in the input field, the key is logged to the console.

Summary

In this tutorial, we discussed the concept of Javascript events, how to trigger them and handle them using event handlers and event listeners.

For further learning, you can look into more complex event types and how to use event delegation for efficient event handling.

Practice Exercises

1. Create a web page with a button that, when clicked, changes the text of a <p> element.
2. Create a web page with an input field that logs every key press to the console.
3. Create a web page with a div that changes its background color to blue when the mouse pointer is over it and changes it back to white when the mouse pointer leaves.

Solutions can be found by applying the concepts and code examples discussed in this tutorial. Remember, practice is key to mastering any programming language or concept.