What is HTML5 Drag and Drop?

HTML5, CSS and JavaScript should be efficiently combined with semantic tags, reasonable loading order and decoupling design. 1. Use HTML5 semantic tags, such as improving structural clarity and maintainability, which is conducive to SEO and barrier-free access; 2. CSS should be placed in, use external files and split by module to avoid inline styles and delayed loading problems; 3. JavaScript is recommended to be introduced in front, and use defer or async to load asynchronously to avoid blocking rendering; 4. Reduce strong dependence between the three, drive behavior through data-* attributes and class name control status, and improve collaboration efficiency through unified naming specifications. These methods can effectively optimize page performance and collaborate with teams.

It is a block-level element, suitable for layout; it is an inline element, suitable for wrapping text content. 1. Exclusively occupy a line, width, height and margins can be set, which are often used in structural layout; 2. No line breaks, the size is determined by the content, and is suitable for local text styles or dynamic operations; 3. When choosing, it should be judged based on whether the content needs independent space; 4. It cannot be nested and is not suitable for layout; 5. Priority is given to the use of semantic labels to improve structural clarity and accessibility.

Three points to note for making HTML5 videos smoothly playback: 1. Select a suitable video format, such as MP4, WebM or Ogg, and provide multiple formats or a single format according to the target user's choice; 2. Use adaptive bit rate technology such as HLS or DASH, combined with hls.js or dash.js to achieve automatic clarity switching; 3. Reasonably set preloading policies and server configurations, such as preload attributes, byte range requests, compression and cache, to optimize loading speed and reduce traffic consumption.

HTML5introducednewinputtypesthatenhanceformfunctionalityanduserexperiencebyimprovingvalidation,UI,andmobilekeyboardlayouts.1.emailvalidatesemailaddressesandsupportsmultipleentries.2.urlchecksforvalidwebaddressesandtriggersURL-optimizedkeyboards.3.num

HTML5Canvas is an API for drawing graphics and animations on web pages, combined with GameAPIs to enable feature-rich web games. 1. Set elements and get 2D context; 2. Use JavaScript to draw objects and implement animation loops; 3. Process user input to control the game; 4. Combine APIs such as Gamepad, WebAudio, PointerLock and Fullscreen to improve the interactive experience; 5. Optimize performance and manage resource loading to ensure smooth operation.

To get the user's current location, use the HTML5 GeolocationAPI. This API provides information such as latitude and longitude after user authorization. The core method is getCurrentPosition(), which requires successful and error callbacks to be handled; at the same time, pay attention to the HTTPS prerequisite, user authorization mechanism and error code processing. ① Call getCurrentPosition to get the position once, and an error callback will be triggered if it fails; ② The user must authorize it, otherwise it cannot be obtained and may no longer be prompted; ③ Error processing should distinguish between rejection, timeout, location unavailable, etc.; ④ Enable high-precision, set timeout time, etc., and can be configured through the third parameter; ⑤ The online environment must use HTTPS, otherwise it may be restricted by the browser.

The difference between async and defer is the execution timing of the script. async allows scripts to be downloaded in parallel and executed immediately after downloading, without guaranteeing the execution order; defer executes scripts in order after HTML parsing is completed. Both avoid blocking HTML parsing. Using async is suitable for standalone scripts such as analyzing code; defer is suitable for scenarios where you need to access the DOM or rely on other scripts.

Image not displayed is usually caused by a wrong file path, incorrect file name or extension, HTML syntax issues, or browser cache. 1. Make sure that the src path is consistent with the actual location of the file and use the correct relative path; 2. Check whether the file name case and extension match exactly, and verify whether the image can be loaded by directly entering the URL; 3. Check whether the img tag syntax is correct, ensure that there are no redundant characters and the alt attribute value is appropriate; 4. Try to force refresh the page, clear the cache, or use incognito mode to eliminate cache interference. Troubleshooting in this order can solve most HTML image display problems.