How to Build a Simple Web Component from Scratch
This guide demonstrates building a reusable web component: a simple counter. We'll leverage Custom Elements, Shadow DOM, and HTML Templates. The finished counter will feature buttons to increment and decrement a displayed numerical value.
A complete, runnable version of this code is available here.
Prerequisites:
Familiarity with basic JavaScript and a conceptual understanding of the DOM (Document Object Model) are helpful, though not strictly required.
Project Setup:
Create two files: counter.html (containing the page structure) and counter.js (housing the custom element definition).
counter.html (Initial Structure):
<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width"> <title>Counter Component</title> </head> <body> <script src="counter.js"></script> </body> </html>
Creating the Template (counter.html - Adding the Template):
We'll define the counter's visual structure using an HTML template:
<template id="x-counter"> <button id="min-btn">-</button> <span id="counter-display">0</span> <button id="plus-btn">+</button> </template>
This template won't render directly; it serves as a blueprint for our custom element.
Defining the Custom Element (counter.js):
This JavaScript code defines the counter's functionality:
class XCounter extends HTMLElement {
constructor() {
super();
this.counter = 0;
this.elements = {};
}
connectedCallback() {
const template = document.getElementById("x-counter");
this.attachShadow({ mode: "open" });
this.shadowRoot.appendChild(template.content.cloneNode(true));
this.elements = {
plusBtn: this.shadowRoot.querySelector("#plus-btn"),
minBtn: this.shadowRoot.querySelector("#min-btn"),
counterDisplay: this.shadowRoot.querySelector("#counter-display")
};
this.displayCount();
this.elements.plusBtn.onclick = () => this.increment();
this.elements.minBtn.onclick = () => this.decrement();
}
increment() {
this.counter++;
this.displayCount();
}
decrement() {
this.counter--;
this.displayCount();
}
displayCount() {
this.elements.counterDisplay.textContent = this.counter;
}
}
customElements.define("x-counter", XCounter);This class extends HTMLElement. connectedCallback handles setup when the element is added to the page, including attaching the shadow DOM and event listeners. increment, decrement, and displayCount manage the counter's value and display.
Using the Counter Component (counter.html - Adding the Custom Element):
To use the counter, simply add <x-counter></x-counter> to your HTML.
Styling the Component (counter.js - Adding Styles):
Encapsulate styling within the component using adoptedStyleSheets:
connectedCallback() {
// ... (previous code) ...
const sheet = new CSSStyleSheet();
sheet.replaceSync(this.styles());
this.shadowRoot.adoptedStyleSheets = [sheet];
// ... (rest of connectedCallback) ...
}
styles() {
return `
:host {
display: block;
border: dotted 3px #333;
width: fit-content;
height: fit-content;
padding: 15px;
}
button {
border: solid 1px #333;
padding: 10px;
min-width: 35px;
background: #333;
color: #fff;
cursor: pointer;
}
button:hover {
background: #222;
}
span {
display: inline-block;
padding: 10px;
width: 50px;
text-align: center;
}
`;
}This adds basic styling, contained within the shadow DOM.
Conclusion:
This tutorial demonstrates creating a simple, reusable web component. The use of templates, shadow DOM, and custom elements promotes modularity and maintainability in web development. Remember to replace [here](https://www.php.cn/link/2eac42424d12436bdd6a5b8a88480cc3) with the actual link to your final code.
The above is the detailed content of How to Build a Simple Web Component from Scratch. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
1670
14
1428
52
1329
25
1274
29
1256
24
Python vs. JavaScript: The Learning Curve and Ease of Use
Apr 16, 2025 am 12:12 AM
Python is more suitable for beginners, with a smooth learning curve and concise syntax; JavaScript is suitable for front-end development, with a steep learning curve and flexible syntax. 1. Python syntax is intuitive and suitable for data science and back-end development. 2. JavaScript is flexible and widely used in front-end and server-side programming.
From C/C to JavaScript: How It All Works
Apr 14, 2025 am 12:05 AM
The shift from C/C to JavaScript requires adapting to dynamic typing, garbage collection and asynchronous programming. 1) C/C is a statically typed language that requires manual memory management, while JavaScript is dynamically typed and garbage collection is automatically processed. 2) C/C needs to be compiled into machine code, while JavaScript is an interpreted language. 3) JavaScript introduces concepts such as closures, prototype chains and Promise, which enhances flexibility and asynchronous programming capabilities.
JavaScript and the Web: Core Functionality and Use Cases
Apr 18, 2025 am 12:19 AM
The main uses of JavaScript in web development include client interaction, form verification and asynchronous communication. 1) Dynamic content update and user interaction through DOM operations; 2) Client verification is carried out before the user submits data to improve the user experience; 3) Refreshless communication with the server is achieved through AJAX technology.
JavaScript in Action: Real-World Examples and Projects
Apr 19, 2025 am 12:13 AM
JavaScript's application in the real world includes front-end and back-end development. 1) Display front-end applications by building a TODO list application, involving DOM operations and event processing. 2) Build RESTfulAPI through Node.js and Express to demonstrate back-end applications.
Understanding the JavaScript Engine: Implementation Details
Apr 17, 2025 am 12:05 AM
Understanding how JavaScript engine works internally is important to developers because it helps write more efficient code and understand performance bottlenecks and optimization strategies. 1) The engine's workflow includes three stages: parsing, compiling and execution; 2) During the execution process, the engine will perform dynamic optimization, such as inline cache and hidden classes; 3) Best practices include avoiding global variables, optimizing loops, using const and lets, and avoiding excessive use of closures.
Python vs. JavaScript: Community, Libraries, and Resources
Apr 15, 2025 am 12:16 AM
Python and JavaScript have their own advantages and disadvantages in terms of community, libraries and resources. 1) The Python community is friendly and suitable for beginners, but the front-end development resources are not as rich as JavaScript. 2) Python is powerful in data science and machine learning libraries, while JavaScript is better in front-end development libraries and frameworks. 3) Both have rich learning resources, but Python is suitable for starting with official documents, while JavaScript is better with MDNWebDocs. The choice should be based on project needs and personal interests.
Python vs. JavaScript: Development Environments and Tools
Apr 26, 2025 am 12:09 AM
Both Python and JavaScript's choices in development environments are important. 1) Python's development environment includes PyCharm, JupyterNotebook and Anaconda, which are suitable for data science and rapid prototyping. 2) The development environment of JavaScript includes Node.js, VSCode and Webpack, which are suitable for front-end and back-end development. Choosing the right tools according to project needs can improve development efficiency and project success rate.
The Role of C/C in JavaScript Interpreters and Compilers
Apr 20, 2025 am 12:01 AM
C and C play a vital role in the JavaScript engine, mainly used to implement interpreters and JIT compilers. 1) C is used to parse JavaScript source code and generate an abstract syntax tree. 2) C is responsible for generating and executing bytecode. 3) C implements the JIT compiler, optimizes and compiles hot-spot code at runtime, and significantly improves the execution efficiency of JavaScript.
