


repaint (repaint), when repaint changes, the element The appearance is changed, and it occurs without changing the layout. For example, changing the outline, visibility, and background color will not affect the rendering of the DOM structure.
reflow (rendering), the difference from repaint is that it will affect the rendering of the dom structure, and at the same time it will trigger repaint, it will change itself and all parent elements (ancestors), this overhead is very expensive, resulting in performance The decline is inevitable, and the more page elements there are, the more obvious the effect will be.
When it happens:
. Addition, modification (content), deletion (Reflow Repaint) of DOM elements
. Only modify the font color of DOM elements (only Repaint, because there is no need to adjust the layout)
. Apply new styles or modify any properties that affect the appearance of the element
. Resize browser windows, scroll pages
. Read certain properties of the element (offsetLeft, offsetTop, offsetHeight, offsetWidth, scrollTop/Left/Width/ Height, clientTop/Left/Width/Height, getComputedStyle(), currentStyle(in IE))
How to avoid:
. Delete the element from the document first, and then put the element back to its original position after completing the modification.
. Set the display of the element to "none", and then modify the display after completing the modification. is the original value
. If you need to create multiple DOM nodes, you can use DocumentFragment to create them and add them to the document at once
var fragment = document.createDocumentFragment();
fragment.appendChild(document.createTextNode('keenboy test 111'));
fragment.appendChild(document.createElement('br'));
fragment.appendChild(document.createTextNode('keenboy test 222'));
document.body.appendChild(fragment);
. Focus on modifying the style
4.1 Modify the attributes on the element style as little as possible
4.2 Try to modify the style by modifying the className
4.3 Set the style value through the cssText attribute
element.style.width=”80px”; //reflow
element.style.height=”90px” ; //reflow
element.style.border=”solid 1px red”; //reflow
The above will generate multiple reflows. The more calls are made, the more
element.style.cssText=” width:80px;height:80px;border:solid 1px red;”; //reflow
4.4 Caching Layout attribute value
var left=elem.offsetLeft; Using left multiple times will generate a reflow
4.5 Set the position of the element to absolute or fixed
The element is separated from the standard flow and also separated from the DOM tree structure. When reflow is needed, only reflow itself and subordinate elements
4.6 Try not to use table layout
table element Once reflow is triggered, it will cause all other elements in the table to reflow. When tables are suitable for use, you can set table-layout to auto or fixed, so that the table can be rendered line by line. This approach is also to limit the scope of influence of reflow
4.7 Avoid using expression, which will be displayed every time it is called. Recalculate again (including loading page)
Reference:
Yahoo! Performance Engineer Nicole Sullivan's latest article "Reflows & Repaints: CSS Performance making your JavaScript slow?"

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.

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 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.

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'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.


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

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

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.

EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function

SAP NetWeaver Server Adapter for Eclipse
Integrate Eclipse with SAP NetWeaver application server.

Dreamweaver Mac version
Visual web development tools
