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ARIAattributesenhancewebaccessibilityforuserswithdisabilitiesbyprovidingadditionalsemanticinformationtoassistivetechnologies.TheyareneededbecausemodernJavaScript-heavycomponentsoftenlackthebuilt-inaccessibilityfeaturesofnativeHTMLelements,andARIAfill

React itself does not directly manage focus or accessibility, but provides tools to effectively deal with these issues. 1. Use Refs to programmatically manage focus, such as setting element focus through useRef; 2. Use ARIA attributes to improve accessibility, such as defining the structure and state of tab components; 3. Pay attention to keyboard navigation to ensure that the focus logic in components such as modal boxes is clear; 4. Try to use native HTML elements to reduce the workload and error risk of custom implementation; 5. React assists accessibility by controlling the DOM and adding ARIA attributes, but the correct use still depends on developers.

Let’s talk about the key points directly: Merging resources, reducing dependencies, and utilizing caches are the core methods to reduce HTTP requests. 1. Merge CSS and JavaScript files, merge files in the production environment through building tools, and retain the development modular structure; 2. Use picture Sprite or inline Base64 pictures to reduce the number of image requests, which is suitable for static small icons; 3. Set browser caching strategy, and accelerate resource loading with CDN to speed up resource loading, improve access speed and disperse server pressure; 4. Delay loading non-critical resources, such as using loading="lazy" or asynchronous loading scripts, reduce initial requests, and be careful not to affect user experience. These methods can significantly optimize web page loading performance, especially on mobile or poor network

CSS transitions enable switching between CSS attribute values ​​through smooth animations, which are suitable for user interaction scenarios such as button hovering effects, menu expansion and collapse. Common usages include button closure effect, drop-down menu gradient, background color gradient, image transparency or zoom changes. The basic syntax is a transition: attribute duration time sequence function, which can specify a single or multiple attributes, or all can be used to represent all attributes, but it should be used with caution. Timing functions such as ease, linear, and ease-in-out control the animation speed curve, and can also be customized by cubic-bezier. It is recommended to prioritize opacity and transform for better performance, combined with @media(prefers-

To center a div horizontally and vertically, 1. Use Flexbox: the parent container sets display:flex, justify-content and align-items as center; 2. Use Grid: the parent container sets display:grid, place-items as center; 3. Absolute positioning and transform: the child elements are set to absolute, top and left are 50%, and then translate-50%. It should be noted that margin:0auto can only achieve horizontal centering.

Shallowrenderingtestsacomponentinisolation,withoutchildren,whilefullrenderingincludesallchildcomponents.Shallowrenderingisgoodfortestingacomponent’sownlogicandmarkup,offeringfasterexecutionandisolationfromchildbehavior,butlacksfulllifecycleandDOMinte

StrictMode does not render any visual content in React, but it is very useful during development. Its main function is to help developers identify potential problems, especially those that may cause bugs or unexpected behavior in complex applications. Specifically, it flags unsafe lifecycle methods, recognizes side effects in render functions, and warns about the use of old string refAPI. In addition, it can expose these side effects by intentionally repeating calls to certain functions, thereby prompting developers to move related operations to appropriate locations, such as the useEffect hook. At the same time, it encourages the use of newer ref methods such as useRef or callback ref instead of string ref. To use Stri effectively

Create TypeScript-enabled projects using VueCLI or Vite, which can be quickly initialized through interactive selection features or using templates. Use tags in components to implement type inference with defineComponent, and it is recommended to explicitly declare props and emits types, and use interface or type to define complex structures. It is recommended to explicitly label types when using ref and reactive in setup functions to improve code maintainability and collaboration efficiency.