Analysis of JavaScript's Judgment and Processing of Numbers
This article mainly introduces JavaScript's method of judging and processing numbers. It analyzes common methods of judging numbers and techniques for number processing in JavaScript with examples. It has certain reference value. Friends who need it can refer to it. The specific analysis is as follows :
The polymorphic attributes of Javascript are very cool. A var does not need to remember so many strange variables. However, sometimes you will be confused, why, I am obviously adding two numbers, But what if the results are added as strings? This is the disadvantage of Javascript's var. Unlike php, it uses a . to indicate that this is a string connection. This is where you need parseFloat to explicitly indicate that this var is a number. You need to use isNaN to determine whether this is a number. When isNaN (a judged var), if the result is true, then it is not a number. If the result is false, then it is a number. Note here.
The following is such a program. If you input two numbers, you can add them normally. If any of the input numbers is not a number, then a prompt will pop up. If the two input numbers are numbers, the result will pop up. It’s worth it. Note that in Javascript, 00000.22 will also be considered a number, which is 0.22
This program is written like this. Also note that in addition to judging whether num1 or num2 is While counting, you must also prevent the user from clicking the cancel button! :
<html>
<head>
<meta http-equiv="content-type" content="text/html;charset=utf-8"/>
</head>
<body>
</body>
</html>
<script>
var num1=window.prompt("请输入一个数");
var num2=window.prompt("请输入第二个数");
if(isNaN(num1)||isNaN(num2)||!num1||!num2)
alert("任意一个不是数！");
else{
var res=parseFloat(num1)+parseFloat(num2);
alert("两数相加的结果是："+res);
}
document.write("程序已经运行完毕，大家散了吧！");
</script>window.prompt can pop up an input box. Although it is rarely used in today’s web pages and is almost invisible, then follow the above process and finally use document.write. Output information on the web page in an overlay manner. The so-called output information in an overlay manner means that no matter what content is on the web page, it will be overwritten by the content in document.write. This method is rarely used now.
The above is the entire content of this chapter. For more related tutorials, please visit JavaScript Video Tutorial!
JavaScript in Action: Real-World Examples and ProjectsApr 19, 2025 am 12:13 AMJavaScript'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.
JavaScript and the Web: Core Functionality and Use CasesApr 18, 2025 am 12:19 AMThe 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.
Understanding the JavaScript Engine: Implementation DetailsApr 17, 2025 am 12:05 AMUnderstanding 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: The Learning Curve and Ease of UseApr 16, 2025 am 12:12 AMPython 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.
Python vs. JavaScript: Community, Libraries, and ResourcesApr 15, 2025 am 12:16 AMPython 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.
From C/C to JavaScript: How It All WorksApr 14, 2025 am 12:05 AMThe 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 Engines: Comparing ImplementationsApr 13, 2025 am 12:05 AMDifferent JavaScript engines have different effects when parsing and executing JavaScript code, because the implementation principles and optimization strategies of each engine differ. 1. Lexical analysis: convert source code into lexical unit. 2. Grammar analysis: Generate an abstract syntax tree. 3. Optimization and compilation: Generate machine code through the JIT compiler. 4. Execute: Run the machine code. V8 engine optimizes through instant compilation and hidden class, SpiderMonkey uses a type inference system, resulting in different performance performance on the same code.
Beyond the Browser: JavaScript in the Real WorldApr 12, 2025 am 12:06 AMJavaScript's applications in the real world include server-side programming, mobile application development and Internet of Things control: 1. Server-side programming is realized through Node.js, suitable for high concurrent request processing. 2. Mobile application development is carried out through ReactNative and supports cross-platform deployment. 3. Used for IoT device control through Johnny-Five library, suitable for hardware interaction.
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
SublimeText3 Chinese version
Chinese version, very easy to use
VSCode Windows 64-bit Download
A free and powerful IDE editor launched by Microsoft
EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function
WebStorm Mac version
Useful JavaScript development tools
MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.
