1. Introduction

In this tutorial, we aim to understand how to select and manipulate the Document Object Model (DOM) elements using JavaScript. This is an essential skill as it enables you to make your web pages interactive and dynamic.

By the end of this tutorial, you will learn:

• How to select DOM elements using various methods
• How to manipulate the selected DOM elements

Prior experience with HTML and a basic understanding of JavaScript is beneficial for this tutorial.

2. Step-by-Step Guide

DOM Selection

The first step in manipulating DOM elements is to select the element. There are various methods to select DOM elements:

• getElementById(): Selects an element by its ID.
• getElementsByClassName(): Selects elements by their class name.
• getElementsByTagName(): Selects elements by their tag name.
• querySelector(): Selects the first element that matches a specified CSS selector(s).
• querySelectorAll(): Selects all elements that match a specified CSS selector(s).

DOM Manipulation

After selecting the DOM element, you can manipulate it in various ways:

• Changing the content using innerHTML, textContent, or value.
• Changing the style of an element using style.
• Changing the attribute of an element using setAttribute().
• Adding or removing classes using classList.add(), classList.remove(), or classList.toggle().

3. Code Examples

Example 1: Selecting Element by ID

// HTML
<div id="myDiv">Hello World!</div>

// JavaScript
let myElement = document.getElementById('myDiv');
console.log(myElement); // Logs the div element

In the above example, getElementById('myDiv') selects the div with the ID 'myDiv'. The selected element is then logged to the console.

Example 2: Changing Content of an Element

// HTML
<div id="myDiv">Hello World!</div>

// JavaScript
let myElement = document.getElementById('myDiv');
myElement.textContent = 'Hello Universe!';

In this example, textContent changes the content of the selected div to 'Hello Universe!'.

4. Summary

In this tutorial, we covered how to select DOM elements using JavaScript and how to manipulate the selected elements. This included changing the content, style and attributes of elements, and adding or removing classes.

Next, you should learn about handling events in JavaScript, which often involves selecting and manipulating DOM elements.

Additional resources:
- MDN Web Docs - Document Object Model (DOM)
- JavaScript.info - DOM manipulation

5. Practice Exercises

1. Select the element with the ID 'test' and change its text content to 'I am the test element'.

Solution:

let testElement = document.getElementById('test');
testElement.textContent = 'I am the test element';

1. Select all elements with the class 'blue' and change their color to blue.

Solution:

let blueElements = document.getElementsByClassName('blue');
for(let i = 0; i < blueElements.length; i++) {
  blueElements[i].style.color = 'blue';
}

Remember, practice makes perfect. So, keep experimenting and coding!