JavaScript input value calculation
JavaScript is a commonly used web programming language that can be used to achieve a variety of interactive effects. This article will introduce how to use JavaScript to input the radius of a circle, and then calculate and output its area and circumference.
1. Enter the radius
Inputting the radius is the first step for us to calculate the circumference and area of a circle. This can be achieved with a simple HTML page. First, we need to create a text box and a button in an HTML file to enter the radius and start calculation. The code is as follows:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>求圆面积和周长</title>
</head>
<body>
<p>请输入圆的半径：</p>
<input type="number" id="radius"></input>
<button onclick="calculate()">计算</button>
<p id="area"></p>
<p id="circumference"></p>
<script src="circle.js"></script>
</body>
</html>This HTML page contains a text box and a calculation button, and also contains two A blank paragraph is used to output the results. Among them, the ID of the text box is "radius", which is used to obtain the radius input value. The button's onclick event is bound to a JavaScript function "calculate()", which is used to calculate the circumference and area of a circle. The results will be output in two paragraphs, represented by tags with IDs "area" and "circumference" respectively.
2. Calculate area and perimeter
In the HTML file, we introduced a JavaScript file named "circle.js". In this file we will write functions for calculating the area and circumference of a circle. The code is as follows:
function calculate() {
var radius = document.getElementById("radius").value;
// 计算面积
var area = Math.PI * Math.pow(radius, 2);
document.getElementById("area").innerHTML = "面积: " + area + "平方厘米";
// 计算周长
var circumference = 2 * Math.PI * radius;
document.getElementById("circumference").innerHTML = "周长: " + circumference + "厘米";
}This function has three main steps. First, it uses JavaScript's DOM methods to get the value of the text box, which is the radius of the circle entered by the user. It then calculates the area of the circle using the PI constant and the pow() function from the Math library. Finally, it calculates the circumference of the circle using the Math library and the entered radius, and outputs the results to two paragraphs in an HTML page. In this example, we're outputting the area and perimeter as strings, but you can format them as needed.
3. Testing and Expansion
We can now open the HTML file in the browser and start testing. Enter a value in the text box, then click the "Calculate" button, and the page will output the area and circumference of the circle. As shown in the figure below:
#You can try to change the input value and click the "Calculate" button multiple times to test the correctness of the calculation function. Additionally, you can extend this simple JavaScript program to accept and output other variables, or provide more complex interactive options to the user.
Conclusion
In this article, we introduced how to use JavaScript to enter the radius of a circle and calculate its area and circumference. JavaScript is a common tool for performing such interactive operations. It can easily manipulate HTML and other browser APIs, which makes writing web applications and web pages easier and more fun.
The above is the detailed content of JavaScript input value calculation. 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
React's Role in HTML: Enhancing User Experience
Apr 09, 2025 am 12:11 AM
React combines JSX and HTML to improve user experience. 1) JSX embeds HTML to make development more intuitive. 2) The virtual DOM mechanism optimizes performance and reduces DOM operations. 3) Component-based management UI to improve maintainability. 4) State management and event processing enhance interactivity.
React and the Frontend: Building Interactive Experiences
Apr 11, 2025 am 12:02 AM
React is the preferred tool for building interactive front-end experiences. 1) React simplifies UI development through componentization and virtual DOM. 2) Components are divided into function components and class components. Function components are simpler and class components provide more life cycle methods. 3) The working principle of React relies on virtual DOM and reconciliation algorithm to improve performance. 4) State management uses useState or this.state, and life cycle methods such as componentDidMount are used for specific logic. 5) Basic usage includes creating components and managing state, and advanced usage involves custom hooks and performance optimization. 6) Common errors include improper status updates and performance issues, debugging skills include using ReactDevTools and Excellent
What are the limitations of Vue 2's reactivity system with regard to array and object changes?
Mar 25, 2025 pm 02:07 PM
Vue 2's reactivity system struggles with direct array index setting, length modification, and object property addition/deletion. Developers can use Vue's mutation methods and Vue.set() to ensure reactivity.
React Components: Creating Reusable Elements in HTML
Apr 08, 2025 pm 05:53 PM
React components can be defined by functions or classes, encapsulating UI logic and accepting input data through props. 1) Define components: Use functions or classes to return React elements. 2) Rendering component: React calls render method or executes function component. 3) Multiplexing components: pass data through props to build a complex UI. The lifecycle approach of components allows logic to be executed at different stages, improving development efficiency and code maintainability.
What are the benefits of using TypeScript with React?
Mar 27, 2025 pm 05:43 PM
TypeScript enhances React development by providing type safety, improving code quality, and offering better IDE support, thus reducing errors and improving maintainability.
How can you use useReducer for complex state management?
Mar 26, 2025 pm 06:29 PM
The article explains using useReducer for complex state management in React, detailing its benefits over useState and how to integrate it with useEffect for side effects.
React and the Frontend Stack: The Tools and Technologies
Apr 10, 2025 am 09:34 AM
React is a JavaScript library for building user interfaces, with its core components and state management. 1) Simplify UI development through componentization and state management. 2) The working principle includes reconciliation and rendering, and optimization can be implemented through React.memo and useMemo. 3) The basic usage is to create and render components, and the advanced usage includes using Hooks and ContextAPI. 4) Common errors such as improper status update, you can use ReactDevTools to debug. 5) Performance optimization includes using React.memo, virtualization lists and CodeSplitting, and keeping code readable and maintainable is best practice.
What are functional components in Vue.js? When are they useful?
Mar 25, 2025 pm 01:54 PM
Functional components in Vue.js are stateless, lightweight, and lack lifecycle hooks, ideal for rendering pure data and optimizing performance. They differ from stateful components by not having state or reactivity, using render functions directly, a
