Variables in JavaScript are "containers" used to store information; JavaScript variables can be used to store values and expressions; JavaScript variables can also store other data types, such as text values.
The operating environment of this article: windows7 system, javascript version 1.8.5, Dell G3 computer.
The meaning of javascript variables
Variables are "containers" used to store information.
Example
var x=5; var y=6; var z=x+y;
Just like algebra
x=5 y=6 z=x+y
In algebra, we use letters (like x) to hold values (like 5).
With the above expression z=x y, we can calculate the value of z to be 11.
In JavaScript, these letters are called variables.
lamp You can think of variables as containers for storing data.
JavaScript Variables
Like algebra, JavaScript variables can be used to store values (such as x=5) and expressions (such as z=x y).
Variables can use short names (such as x and y) or more descriptive names (such as age, sum, totalvolume).
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)
lamp JavaScript statements and JavaScript variables are both case-sensitive.
JavaScript Data Types
JavaScript variables can also hold other data types, such as text values (name="Bill Gates").
In JavaScript, a text like "Bill Gates" is called a string.
JavaScript variables come in many types, but for now, we’ll just focus on numbers and strings.
When you assign a text value to a variable, you should surround the value with double or single quotes.
Do not use quotation marks when the value you assign to a variable is a numeric value. If you surround a numeric value with quotes, the value is treated as text.
Example
var pi=3.14; // 如果你熟悉 ES6,pi 可以使用 const 关键字,表示一个常量 // const pi = 3.14; var person="John Doe"; var answer='Yes I am!';
Declaring (Creating) JavaScript Variables
Creating a variable in JavaScript is often called "declaring" a variable.
We use the var keyword to declare a variable:
var carname;
After a variable is declared, the variable is empty (it has no value).
To assign a value to a variable, use the equal sign:
carname="Volvo";
However, you can also assign a value to a variable when you declare it:
var carname="Volvo";
In the following example, We create a variable named carname, assign it the value "Volvo", and then put it into the HTML paragraph with id="demo":
Example
var carname="Volvo"; document.getElementById("demo").innerHTML=carname;
[Related recommendations: javascript advanced tutorial】
The above is the detailed content of The meaning of javascript variables. For more information, please follow other related articles on the PHP Chinese website!

The differences in performance and efficiency between Python and JavaScript are mainly reflected in: 1) As an interpreted language, Python runs slowly but has high development efficiency and is suitable for rapid prototype development; 2) JavaScript is limited to single thread in the browser, but multi-threading and asynchronous I/O can be used to improve performance in Node.js, and both have advantages in actual projects.

JavaScript originated in 1995 and was created by Brandon Ike, and realized the language into C. 1.C language provides high performance and system-level programming capabilities for JavaScript. 2. JavaScript's memory management and performance optimization rely on C language. 3. The cross-platform feature of C language helps JavaScript run efficiently on different operating systems.

JavaScript runs in browsers and Node.js environments and relies on the JavaScript engine to parse and execute code. 1) Generate abstract syntax tree (AST) in the parsing stage; 2) convert AST into bytecode or machine code in the compilation stage; 3) execute the compiled code in the execution stage.

The future trends of Python and JavaScript include: 1. Python will consolidate its position in the fields of scientific computing and AI, 2. JavaScript will promote the development of web technology, 3. Cross-platform development will become a hot topic, and 4. Performance optimization will be the focus. Both will continue to expand application scenarios in their respective fields and make more breakthroughs in performance.

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.

Yes, the engine core of JavaScript is written in C. 1) The C language provides efficient performance and underlying control, which is suitable for the development of JavaScript engine. 2) Taking the V8 engine as an example, its core is written in C, combining the efficiency and object-oriented characteristics of C. 3) The working principle of the JavaScript engine includes parsing, compiling and execution, and the C language plays a key role in these processes.

JavaScript is at the heart of modern websites because it enhances the interactivity and dynamicity of web pages. 1) It allows to change content without refreshing the page, 2) manipulate web pages through DOMAPI, 3) support complex interactive effects such as animation and drag-and-drop, 4) optimize performance and best practices to improve user experience.

C and JavaScript achieve interoperability through WebAssembly. 1) C code is compiled into WebAssembly module and introduced into JavaScript environment to enhance computing power. 2) In game development, C handles physics engines and graphics rendering, and JavaScript is responsible for game logic and user interface.


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

Atom editor mac version download
The most popular open source editor

VSCode Windows 64-bit Download
A free and powerful IDE editor launched by Microsoft

Zend Studio 13.0.1
Powerful PHP integrated development environment

SublimeText3 English version
Recommended: Win version, supports code prompts!

Notepad++7.3.1
Easy-to-use and free code editor
