What is the loading='lazy' one of the html attributes and how does it improve page performance?

Native lazy loading is a built-in browser function that enables lazy loading of pictures by adding loading="lazy" attribute to the tag. 1. It does not require JavaScript or third-party libraries, and is used directly in HTML; 2. It is suitable for pictures that are not displayed on the first screen below the page, picture gallery scrolling add-ons and large picture resources; 3. It is not suitable for pictures with first screen or display:none; 4. When using it, a suitable placeholder should be set to avoid layout jitter; 5. It should optimize responsive image loading in combination with srcset and sizes attributes; 6. Compatibility issues need to be considered. Some old browsers do not support it. They can be used through feature detection and combined with JavaScript solutions.

srcset and sizes are key properties for HTML implementation of responsive images. srcset provides multiple image sources and their width or pixel density, such as 400w and 800w, and the browser selects the appropriate image accordingly; sizes defines the display width of the image under different screen widths, such as (max-width: 600px)100vw, 50vw, so that the browser can more accurately match the image size. In actual use, you need to prepare multi-size pictures, clearly named, design layout in accordance with media query, and test the performance of the equipment to avoid ignoring sizes or unit errors, thereby saving bandwidth and improving performance.

Using HTML tags, you can use the href attribute to realize page jump, open new windows, positioning within pages and email and phone link functions. 1. Basic usage: Specify the target address through href, such as accessing a web page; 2. Open a new window: add target="_blank" and rel="noopener" attributes; 3. Jump within the page: combine id and # symbol to achieve anchor point positioning; 4. Email phone link: use mailto: or tel: protocol to trigger system applications.

The main difference is that textarea supports multiple lines of text input, while inputtext is only available in a single line. 1. Use inputtype="text" to be suitable for short and single-line user input, such as username, email address, etc., and can set maxlength to limit the number of characters. The browser provides automatic filling function, making it easier to uniformly style across browsers; 2. Use textarea for scenarios that require multiple lines of input, such as comment boxes, feedback forms, support line breaks and paragraphs, and can control the size through CSS or disable the adjustment function. Both support form features such as placeholders and required fills, but textarea defines the size through rows and cols, and input uses the size attribute.

The key steps to implement the draggable function include: 1. Use the draggable attribute of HTML5 to make the elements draggable; 2. Set drag data through the dragstart event; 3. Listen to the dragover and drop event processing placement logic in the target area; 4. Use the FileList object to implement drag and drop upload. The HTML5 native drag and drop API uses a series of event control processes, such as dragstart, dragover, drop, etc., where draggable custom elements need to be set to set draggable="true" and bind dragstart event, and call setData() to save data. The dr must be blocked when handling drag and drop

It is a block-level element, used to divide large block content areas; it is an inline element, suitable for wrapping small segments of text or content fragments. The specific differences are as follows: 1. Exclusively occupy a row, width and height, inner and outer margins can be set, which are often used in layout structures such as headers, sidebars, etc.; 2. Do not wrap lines, only occupy the content width, and are used for local style control such as discoloration, bolding, etc.; 3. In terms of usage scenarios, it is suitable for the layout and structure organization of the overall area, and is used for small-scale style adjustments that do not affect the overall layout; 4. When nesting, it can contain any elements, and block-level elements should not be nested inside.

When writing web content, you need to pay attention to the title and paragraph structure to improve the reading experience and SEO effect. 1. The title level should be clear. A page should only use one h1 as the main title, h2 as the title of the big section, and h3 subdivides the subsections to avoid multiple h1, skip grades or keyword piles up; 2. The paragraph should be controlled in three to four lines, and the key points should be directly mentioned at the beginning, and if necessary, use the ul list to enhance readability; 3. Appropriately use the subtitles of h2 and h3 to guide readers' attention, facilitate information search and optimize search engine recognition.

Is a placeholder for content distribution in WebComponents, allowing content within custom component tags to be inserted into the specified location of the component template. 1. The default slot receives content from unspecified locations; 2. The named slot distinguishes multiple slot areas through the name attribute; 3. The slot can set back content to display default information when content is not passed in; 4. The slot content scope belongs to the parent component, and attention should be paid to browser compatibility and structural nesting issues. Mastered use can improve component flexibility and reusability, but common mistakes include missing slot attributes or inappropriate access to slot content.