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Browser Extensions Development (Chrome & Edge) · Pelajaran

Memodifikasi DOM Halaman Web

Manipulasi Document Object Model (DOM) halaman web dengan menambahkan, menghapus, atau mengubah elemen serta atributnya.

Memodifikasi DOM Halaman Web adalah pelajaran Browser Extensions Development (Chrome & Edge) gratis di CoddyKit. Ini adalah pelajaran 2 dari 4. Kamu bisa membaca pelajaran lengkapnya di bawah secara gratis — lalu praktikkan langsung di browser dengan editor kode bawaan dan tutor AI 24/7. Ini adalah bagian dari jalur belajar Browser Extensions Development (Chrome & Edge), dan progresmu tersinkronisasi di web dan aplikasi CoddyKit. Kursus Browser Extensions Development (Chrome & Edge) mencakup 4 pelajaran total.

Bagian dari pelajaran ini belum diterjemahkan dan ditampilkan dalam bahasa Inggris.

Intro to DOM Modification

Welcome to modifying web page content! This lesson teaches you how to change what users see on a website using your extension.

We'll dive into the Document Object Model (DOM), which is like a tree structure representing all the elements on a web page. Your extension's content scripts can interact with this tree.

Finding Elements on a Page

Before you can change an element, you need to find it! JavaScript provides several ways to select elements from the DOM.

  • document.querySelector(): Finds the first element matching a CSS selector.
  • document.querySelectorAll(): Finds all elements matching a CSS selector.
  • document.getElementById(): Finds an element by its unique ID.

These are your primary tools for targeting specific parts of a web page.

Accessing Elements: Demo

Let's see how to grab an element. Imagine a web page has a paragraph with the ID 'myParagraph' and several other paragraphs.

Try running this code:

// This code would run in your content script.
// It assumes a page with a <p id="myParagraph"> and other <p> tags.

const specificParagraph = document.getElementById('myParagraph');
const allParagraphs = document.querySelectorAll('p');

if (specificParagraph) {
  console.log('Found specific paragraph:', specificParagraph.textContent);
}

console.log('Total paragraphs on page:', allParagraphs.length);

// For demonstration, we'll change a dummy element if it exists.
// In a real scenario, this would modify the live page.
const dummyDiv = document.createElement('div');
dummyDiv.id = 'coddykit-output';
document.body.append(dummyDiv);

if (specificParagraph) {
  dummyDiv.textContent = `Found by ID: ${specificParagraph.textContent}. Total Ps: ${allParagraphs.length}`;
} else {
  dummyDiv.textContent = `No #myParagraph found. Total Ps: ${allParagraphs.length}`;
}

Updating Text Content

Once you have an element, changing its text is straightforward. You can use the textContent property.

textContent sets or returns the text content of the specified node and all its descendants. It's generally preferred over innerText for performance and security.

Changing Text: Demo

Let's update the text of the first heading on a page. This is a common task for extensions that want to add information or warnings.

What do you think this will do to the page's main heading?

// This code would run in your content script.
// It assumes the page has at least one <h1> element.

const mainHeading = document.querySelector('h1');

if (mainHeading) {
  mainHeading.textContent = '🥳 This Heading Was Modified by CoddyKit!';
  mainHeading.style.color = 'blue'; // Add some style for visibility
} else {
  // If no h1, create one to show the effect
  const newHeading = document.createElement('h1');
  newHeading.textContent = '🥳 New Heading from CoddyKit!';
  newHeading.style.color = 'blue';
  document.body.prepend(newHeading);
}

Altering Element Attributes

Elements often have attributes like src for images, href for links, or class for styling. You can change these too!

  • element.setAttribute(name, value): Adds or updates an attribute.
  • element.removeAttribute(name): Removes an attribute.
  • element.classList.add(className): Adds a CSS class.
  • element.classList.remove(className): Removes a CSS class.

Attributes & Classes: Demo

Let's change an image's source and add a class to a paragraph. Imagine you want to replace a placeholder image or highlight certain text.

Try running this example:

// This code would run in your content script.
// It assumes a page has an <img> and a <p> element.

const firstImage = document.querySelector('img');
const firstParagraph = document.querySelector('p');

if (firstImage) {
  firstImage.setAttribute('src', 'https://www.google.com/images/branding/googlelogo/1x/googlelogo_color_272x92dp.png');
  firstImage.setAttribute('alt', 'CoddyKit Replaced Image');
  firstImage.style.border = '2px solid green'; // Make changes visible
}

if (firstParagraph) {
  firstParagraph.classList.add('coddykit-highlight');
  // Add some inline style for the added class for visibility
  firstParagraph.style.backgroundColor = '#ffff0050'; // Light yellow tint
  firstParagraph.style.padding = '5px';
  firstParagraph.textContent += ' (Highlighted by CoddyKit!)';
} else {
  const newP = document.createElement('p');
  newP.textContent = 'This is a new paragraph with a highlight!';
  newP.classList.add('coddykit-highlight');
  newP.style.backgroundColor = '#ffff0050';
  newP.style.padding = '5px';
  document.body.append(newP);
}

Creating & Adding New Elements

Extensions can also inject entirely new content into a page! This is how you might add custom buttons, sidebars, or notifications.

  • document.createElement(tagName): Creates a new element node.
  • parentNode.appendChild(childNode): Adds a node as the last child of a parent.
  • parentNode.prepend(childNode): Adds a node as the first child of a parent.
  • parentNode.insertBefore(newNode, referenceNode): Inserts a node before a reference node.

Injecting Elements: Demo

Let's create a new div element and add it to the very top of the web page's body.

This demonstrates how an extension can seamlessly integrate new UI elements.

// This code would run in your content script.

const newDiv = document.createElement('div');
newDiv.textContent = '👋 Hello from your CoddyKit Extension!';
newDiv.style.backgroundColor = '#ADD8E6'; // Light blue background
newDiv.style.padding = '10px';
newDiv.style.textAlign = 'center';
newDiv.style.borderBottom = '1px solid #87CEEB';
newDiv.style.position = 'sticky';
newDiv.style.top = '0';
newDiv.style.width = '100%';
newDiv.style.zIndex = '9999';

document.body.prepend(newDiv); // Add to the top of the body

// You can also remove elements:
// const elementToRemove = document.querySelector('.some-ad-class');
// if (elementToRemove) {
//   elementToRemove.remove();
// }

Quick Check: DOM Actions

Which of the following JavaScript methods can be used to add, remove, or modify elements on a web page?

Recap: Modifying Web Pages

Great job! You've learned the core techniques for interacting with and modifying a web page's structure and content using content scripts.

  • You can find elements using querySelector, querySelectorAll, and getElementById.
  • You can change text with textContent.
  • You can alter attributes and classes with setAttribute, removeAttribute, classList.add, and classList.remove.
  • You can create and inject new elements using createElement and methods like appendChild or prepend.
  • You can remove elements with element.remove().

These powerful tools allow your extension to truly customize the user's browsing experience. Next, we'll explore how to interact with the data on these pages!

Pertanyaan yang Sering Diajukan

Apakah pelajaran “Memodifikasi DOM Halaman Web” gratis?

Ya — teks lengkap “Memodifikasi DOM Halaman Web” gratis dibaca di sini di web. Untuk praktiknya secara interaktif (editor kode bawaan dan tutor AI 24/7) dan buka sisa kursus Browser Extensions Development (Chrome & Edge), upgrade ke CoddyKit PRO. Kursus Browser Extensions Development (Chrome & Edge) mencakup 4 pelajaran total.

Apa yang akan aku pelajari di “Memodifikasi DOM Halaman Web”?

Manipulasi Document Object Model (DOM) halaman web dengan menambahkan, menghapus, atau mengubah elemen serta atributnya. Kamu berlatih Browser Extensions Development (Chrome & Edge) dengan kode praktik yang langsung kamu jalankan di browser, dan tutor AI 24/7 menjawab pertanyaanmu saat kamu mengerjakan pelajaran ini.

Apakah aku perlu pengalaman untuk memulai Browser Extensions Development (Chrome & Edge)?

Tidak diperlukan pengalaman sebelumnya. Browser Extensions Development (Chrome & Edge) di CoddyKit dirancang untuk pemula hingga pelajar tingkat lanjut, jadi kamu bisa memulai di sini atau dari awal dan belajar sesuai kecepatan kamu sendiri. Ini adalah pelajaran 2 dari 4.

Berapa lama pelajaran “Memodifikasi DOM Halaman Web” memakan waktu?

Sebagian besar pelajaran CoddyKit memakan waktu sekitar 5–10 menit. Setiap pelajaran ringkas dan interaktif, jadi kamu membuat kemajuan stabil dan melanjutkan dari tempat kamu tinggalkan di web dan aplikasi.

Bisakah aku menulis dan menjalankan kode dalam pelajaran Browser Extensions Development (Chrome & Edge) ini?

Ya. Setiap pelajaran Browser Extensions Development (Chrome & Edge) menyertakan editor kode bawaan, jadi kamu menulis dan menjalankan kode nyata langsung di browser dan mendapatkan umpan balik AI instan — tidak diperlukan penyiapan lokal.

Semua pelajaran dalam kursus ini

  1. Menyisipkan Skrip Konten
  2. Memodifikasi DOM Halaman Web
  3. Berinteraksi dengan Data Halaman Web
  4. Menyisipkan CSS dan Gaya Terisolasi
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