What is the difference between async and defer for script tags?

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.

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.

To achieve a basic pop-up effect, you need to follow the following steps: 1. Structure: Use HTML to create trigger buttons, mask layer and pop-up content area; 2. Style: Set default hidden, centered layout, mask background and close button styles through CSS; 3. Interaction: Use JavaScript to bind click events to control pop-up display and hide, and can expand the ESC key closing function; 4. Optimization: Add CSS animation to improve user experience. The entire process does not require a third-party library, which is suitable for quickly realizing basic pop-up functions.

Tags are a tag introduced by HTML5 to define reusable content fragments. They are not rendered immediately, but can be dynamically inserted through JavaScript. The usage process includes: 1. Defining the template; 2. Cloning the content; 3. Inserting the DOM. For example, get the template through document.getElementById, call cloneNode(true) and insert the page. When dynamically filling the data, content binding can be achieved by operating the cloned DOM elements, which is suitable for building product lists, user cards and other components. When using it, be careful not to directly access template sub-elements, avoid ID conflicts, handle style scopes, and can also create encapsulation components with WebComponents.

Webworkers are independent threads running in the browser background, used to perform time-consuming tasks without blocking the user interface. They are implemented through JavaScript files and are started by scripts in HTML pages, but once run, they are separated from the main thread. 1. Webworkers cannot directly access the DOM to ensure page stability; 2. They realize secure communication with the main thread through postMessage() and onmessage; 3. It is suitable for processing CPU-intensive tasks such as images, complex computing, data analysis; 4. It supports some APIs such as setTimeout, fetch and IndexedDB; 5. When using it, you need to pay attention to debugging difficulties, memory usage, cross-domain restrictions and other issues.