How to use JavaScript variables-JS Tutorial-php.cn

Home

Web Front-end

JS Tutorial

How to use JavaScript variables

不言

Dec 12, 2018 pm 05:44 PM

When writing a program, we need to use various data in each place. Sometimes we also need to reuse strings and the same values and calculation formulas. If we write them all, it will be very troublesome. At this time, the variables It will be very useful.

How to use JavaScript variables

First let’s take a look at what JavaScript variables are?

JavaScript variables can be used to store values (such as x=2) and expressions (such as z=x y). Variables can have short names (such as x and y) or more descriptive names.

Variables must start with a letter

Variables can also start with $ and _ symbols (but we do not recommend this)

Variable names are case-sensitive (y and Y are different variables)

Then let’s take a look at how to use JavaScript variables

The writing method of variables in JavaScript is as follows

var How to use JavaScript variables名 = “值、字符串”;

When using var to complete the variable declaration, replace the value and string data attached to the right side "" with the variable on the left side, and use the assignment operator "=".

Therefore, if you want to put the string string in a variable named name, you need to perform the following operations

var name = "string"

In addition to var, variables also include let and const. About these three You can refer to the articleThe difference between let, var and const in JavaScript and the introduction of application scenarios, so I won’t go into details here.

Let's use the var variable to see a specific example

In this example, we define "string" as a variable and use document.write method calls it. By using the command document.write(), numerical values and strings can be displayed.

The code is as follows



  
    
    JavaScript
  
  
    <script>
      var name = &quot;string&quot;;
      document.write(name);
    </script>

The running effect on the browser is as follows

How to use JavaScript variables

Finally, we can also implement pop-up boxes Notification

Pop-up notification can be easily implemented in JavaScript, which is helpful when confirming the execution results.

alert(How to use JavaScript variables);

By the way, this time put the calculation formula into the variable and output it. In the case of numbers, since they are not strings, "" is not used.

The code is as follows

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>JavaScript</title>
  </head>
  <body>
    <script>
      var i = 1 + 100;
      alert(i);
    </script>
  </body>
</html>

The operation effect is as follows

How to use JavaScript variables

Assign the value "1 100" to variable i and output the total number .

The above is the detailed content of How to use JavaScript variables. For more information, please follow other related articles on the PHP Chinese website!

Statement

The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

From Websites to Apps: The Diverse Applications of JavaScriptApr 22, 2025 am 12:02 AM

JavaScript is widely used in websites, mobile applications, desktop applications and server-side programming. 1) In website development, JavaScript operates DOM together with HTML and CSS to achieve dynamic effects and supports frameworks such as jQuery and React. 2) Through ReactNative and Ionic, JavaScript is used to develop cross-platform mobile applications. 3) The Electron framework enables JavaScript to build desktop applications. 4) Node.js allows JavaScript to run on the server side and supports high concurrent requests.

Python vs. JavaScript: Use Cases and Applications ComparedApr 21, 2025 am 12:01 AM

Python is more suitable for data science and automation, while JavaScript is more suitable for front-end and full-stack development. 1. Python performs well in data science and machine learning, using libraries such as NumPy and Pandas for data processing and modeling. 2. Python is concise and efficient in automation and scripting. 3. JavaScript is indispensable in front-end development and is used to build dynamic web pages and single-page applications. 4. JavaScript plays a role in back-end development through Node.js and supports full-stack development.

The Role of C/C in JavaScript Interpreters and CompilersApr 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.

JavaScript in Action: Real-World Examples and ProjectsApr 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.

JavaScript and the Web: Core Functionality and Use CasesApr 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.

Understanding the JavaScript Engine: Implementation DetailsApr 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: The Learning Curve and Ease of UseApr 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.

Python vs. JavaScript: Community, Libraries, and ResourcesApr 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.

See all articles