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  • What are shadow DOM and custom elements?
    What are shadow DOM and custom elements?
    ShadowDOM is used to create independent DOM trees to implement style and structure isolation, and CustomElements is used to define custom HTML elements to improve reusability and semantics. 1. ShadowDOM provides style isolation, structural encapsulation and avoid conflicts, and is created through the attachShadow method. 2.CustomElements implements componentization by inheriting the HTMLElement class and registering new tags. 3. The two are often used in combination to create ShadowDOM in the constructor to implement plug-and-play components. 4. Application scenarios include building component libraries, encapsulating third-party components, and modules that require highly isolated. 5. Note that the naming must include short horizontal lines and mode selection affects external access
    HTML Tutorial . Web Front-end 605 2025-06-22 00:54:12
  • What are common HTML attributes (e.g., class, id, style, title, src, href)?
    What are common HTML attributes (e.g., class, id, style, title, src, href)?
    HTML attributes are used to add extra information to tags. Class and id are used for positioning and styles. Class can be reused and id is unique. Style is used for inline styles but is not recommended for large-scale use. Title provides mouse hover prompts. Src introduces external resources such as pictures and scripts, and href specifies link address. Other common attributes include alt, placeholder, target="_blank" and rel="nofollow".
    HTML Tutorial . Web Front-end 675 2025-06-22 00:53:42
  • How do I use the readonly attribute to make an input field read-only?
    How do I use the readonly attribute to make an input field read-only?
    To make the input field read-only, use the readonly property. 1. Add readonly attribute to the input tag to achieve read-only effect; 2. readonly allows users to select and copy content and submit it with the form; 3. Unlike disabled, the latter is not submitted with the form and cannot gain focus; 4. The read-only state can be dynamically controlled through JavaScript, such as setting input.readOnly=true or false; 5. Pay attention to testing form submission behavior, accessibility and visual style when using it to improve user experience.
    HTML Tutorial . Web Front-end 828 2025-06-22 00:52:52
  • How do I use the element to add subtitles or captions to audio and video elements?
    How do I use the element to add subtitles or captions to audio and video elements?
    The key to adding subtitles or titles with elements is to link correctly formatted text files (such as WebVTT) to media elements. 1. Used to specify the timed text track in or, suitable for providing translation, closing subtitles or adding metadata prompts; 2. Before using, make sure that the format of the WebVTT file is correct: the first behavior is WEBVTT, there are two new lines between each prompt block, and the time format is HH:MM:SS.mm; 3. Load subtitles in HTML through attributes such as src, kind, srclang, label, etc., and set default to enable subtitles by default; 4. Common problems include that the browser does not display subtitles, time is out of sync, path errors or offline loading failures, and check the MIME type, time code, and network
    HTML Tutorial . Web Front-end 529 2025-06-22 00:51:41
  • How do I use shadow DOM and custom elements to create web components?
    How do I use shadow DOM and custom elements to create web components?
    ShadowDOM and custom elements are the core of WebComponents for encapsulating standalone HTML, CSS, and JavaScript. 1. ShadowDOM creates an isolated DOM tree through the attachShadow() method to avoid style and logic conflicts; 2. Custom elements register new tags by inheriting HTMLElement and using customElements.define(); 3. Component encapsulation can be implemented in the constructor; 4. Lifecycle callbacks such as connectedCallback and attribute listening to observedAttributes can control component behavior; 5. Note
    HTML Tutorial . Web Front-end 551 2025-06-22 00:50:32
  • What are tags, and what are they used for?
    What are tags, and what are they used for?
    Meta tags have four core functions in HTML pages: 1. Define basic web page information, such as character sets, authors and descriptions; 2. Control the display effect of the mobile terminal and adapt to the viewports of different devices; 3. Provide title, description and image information during social sharing; 4. Control search engine indexing behavior to determine whether the page is included or tracked links.
    HTML Tutorial . Web Front-end 159 2025-06-22 00:48:31
  • How do I use the poster attribute to display a preview image before the video starts playing?
    How do I use the poster attribute to display a preview image before the video starts playing?
    Poster attributes are used in HTML5 to specify the preview image displayed before the video starts playing, which is implemented by adding an image URL to the tag. When using it, you need to ensure the correct path. The picture should be a high-quality keyframe screenshot to avoid blurred or overly dark images, and optimize the loading speed; some browsers or mobile devices may not display posters due to fast video loading, dynamic src or automatic playback restrictions; posters can be scaled through CSS, but the style is restricted directly. Reasonable selection and processing of posters can improve the user experience.
    HTML Tutorial . Web Front-end 867 2025-06-22 00:46:12
  • How do I use the class attribute to apply CSS styles to elements?
    How do I use the class attribute to apply CSS styles to elements?
    To apply CSS styles using classes in HTML, first assign one or more class names to the element through the class attribute, and then define the styles of these classes in CSS. For example: You can use .highlight{background-color:yellow;} to achieve highlighting effect; if multiple classes are needed, you can write it as and define the .box and .warning styles respectively. Classes are suitable for multiplexing styles across elements, creating style variants, and building reusable components. They are more flexible and controllable than ID selectors (unique) and element selectors (specific tags only). When naming classes, they should be concise and clear, avoid being too general, and BEM and other specifications can be used to improve maintainability. Browser efficiently handles class reuse without worrying about sex
    HTML Tutorial . Web Front-end 681 2025-06-22 00:36:42
  • What is the difference between and elements?
    What is the difference between and elements?
    HTMLheadingelementsfromtodifferinsemanticimportanceandvisualappearance.1.isthemostimportant,usedforthemaintitle.2.toserveassubheadingsindescendingorder.3.isleastprominent,oftenforfootnotesorsidebars.SemanticstructureaidsaccessibilityandSEO.Visually,i
    HTML Tutorial . Web Front-end 688 2025-06-22 00:34:11
  • How do I use the title attribute to provide a tooltip for an element?
    How do I use the title attribute to provide a tooltip for an element?
    The most direct way is to use the title attribute of HTML. 1. Add title attribute to the element, such as: title="your prompt text", the browser will automatically display tooltip; 2. Applicable to links, pictures, buttons and other elements, suitable for lightweight prompts; 3. Notes include: not recommended for important content, content will be truncated too long, and cannot include HTML format; 4. Common applicable scenarios include: function description, picture description, form prompts, abbreviation explanation, etc.
    HTML Tutorial . Web Front-end 635 2025-06-22 00:33:42
  • How do I create tables in HTML using the , , , and elements?
    How do I create tables in HTML using the , , , and elements?
    To create an HTML table, first use the tag as the container, then define the rows, and then define the header or data cells through or separately. 1. Use as a table container; 2. Create table rows with use; 3. Use title cells that define bold and centered; 4. Use normal data cells to define normal data cells; 5. Keep the number of cells per row consistent to ensure clear structure; 6. Use CSS to add borders, inner margins and other styles to improve readability; 7. Avoid using tables for page layout, and focus on displaying structured data; 8. Consider responsive design to adapt to small screen display.
    HTML Tutorial . Web Front-end 390 2025-06-22 00:29:52
  • What is the src attribute, and how do I use it to specify the URL of an image?
    What is the src attribute, and how do I use it to specify the URL of an image?
    The src attribute is an attribute in HTML that specifies the source address of the resource, and is commonly found in tags such as, etc. 1. It tells the browser where to load images, scripts, or embed content; 2. You can use relative paths (such as ../images/photo.jpg) or absolute paths (such as full URLs) to specify the resource location; 3. You can also use base64 to encode embedded small images to reduce the number of requests. In addition, you need to pay attention to path case, image format compatibility, URL encoding and adding alt attributes to improve accessibility and SEO.
    HTML Tutorial . Web Front-end 638 2025-06-22 00:22:51
  • What is the href attribute, and how do I use it to specify the URL of a link?
    What is the href attribute, and how do I use it to specify the URL of a link?
    href is a key attribute of tags in HTML that specifies the target address of the link. It determines which URL the browser will jump to when the user clicks on the hyperlink. For example: VisitExample will guide the user to https://example.com. When using href, you should pay attention to distinguish between absolute URLs (such as external website links), relative URLs (such as internal page navigation) and mailto: links (such as email addresses). Common errors include missing quotes, path errors, and missing http:// or https:// prefixes. In addition, href is also used to load style sheets and jump within pages. Proper formatting and verification of href values ??is essential to avoid link breaks, improve user experience and SEO
    HTML Tutorial . Web Front-end 159 2025-06-22 00:19:32
  • What are global attributes in HTML, and can they be used on any element?
    What are global attributes in HTML, and can they be used on any element?
    Yes,globalattributesinHTMLcanbeappliedtoanyelement.Commononesincludeclass,id,style,title,lang,anddata-.Theyareusedforstyling,tooltips,metadata,andaccessibility.Exceptionsincludemisuseoftabindexorcontenteditablewhichmaycauseissues.Tips:usedata-onlywhe
    HTML Tutorial . Web Front-end 383 2025-06-22 00:19:02

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