Jquery's operation on dom is also very necessary.
1. Three simple and practical jQuery methods for DOM operations:
· text() - Set or return the text content of the selected element
· html() - Sets or returns the content of the selected element (including HTML tags)
· val() - Sets or returns the value of the form field
2. attr() gets the attribute . Of course, these two can also be modified by setting the values yourself,
3. Adding html content . Adding new HTML content
We will learn four jQuery methods for adding new content:
· append() - Insert content at the end of the selected element
· prepend() - Insert content
at the beginning of the selected element · after() - Insert content
after the selected element · before() - Insert content
4. Delete elements/content
If you need to delete elements and content, you can generally use the following two jQuery methods:
· remove() - Delete the selected element (and its child elements)
· empty() - delete the child element from the selected element
5.jQuery operation CSS
jQuery has several methods for performing CSS operations. We will study the following:
· addClass() - Add one or more classes to the selected element
· removeClass() - Remove one or more classes from the selected element
· toggleClass() - Add/remove classes to selected elements
· css() - Set or return style attributes
Example
$("h1,h2,p").addClass("blue"); First of all, we know that when adding styles to multiple tags, we use ',' to separate them. Blue must be a set.Blue{} class selector
$("h1,h2,p").removeClass("blue");
$("h1,h2 ,p").toggleClass("blue"); If there is a style, it will be removed. If there is no style, it will be added
6. Set multiple CSS properties
such as To set multiple CSS properties, please use the following syntax:
css({"propertyname":"value","propertyname":"value",...});
7.jQuery size methods
jQuerywidth() and height() methods
width() method sets or returns the width of the element (excluding padding, border or outer edge distance). The
height() method sets or returns the height of an element (not including padding, borders, or margins).
jQueryinnerWidth() and innerHeight() methods
innerWidth() method returns the width of the element (including padding).
The innerHeight() method returns the height of the element (including padding).
jQueryouterWidth() and outerHeight() methods
outerWidth() method returns the width of the element (including padding and borders).
outerHeight() method returns the height of the element (including padding and border).

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 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 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 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.

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.

Different 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.

JavaScript'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.

I built a functional multi-tenant SaaS application (an EdTech app) with your everyday tech tool and you can do the same. First, what’s a multi-tenant SaaS application? Multi-tenant SaaS applications let you serve multiple customers from a sing


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