What is the difference between script src and script defer?
The main difference between script src and script defer is that script src downloads and executes the script immediately, while script defer downloads the script but waits to execute the script until the page has finished parsing. This ensures that the page has been loaded and that any dependent resources have been downloaded before the script starts running.
What are the advantages of using script defer?
2. Synchronization: Script defer ensures that the scripts in deferred tags execute in the order they appear in the HTML document.
3. Non-blocking: Deferred scripts do not block the HTML parser, which eliminates render-blocking issues in the browser.
4. Compatibility: Script defer is supported across all modern web browsers.
What is the difference between script defer and async?
Script defer causes the script to be executed after the document parsing is finished, while async causes the script to be executed as soon as it is downloaded. Async allows scripts to be downloaded and executed in parallel while defer waits until the document is parsed and executed in order.
What is the difference between script defer and script async?
Script defer runs in the order it appears in the page, while script async runs as soon as it is loaded. Deferred scripts are guaranteed to not block the rendering of the page, while async scripts run independently of HTML parsing while they are downloading, so they may block rendering.
Defer and async are two HTML attributes that can be used in script tags to specify the order in which scripts are executed on a page. The defer attribute tells the browser to wait until the page has finished loading before running the script. The async attribute tells the browser to run the script as soon as it is available, without waiting for the page to fully load. Both of these attributes can help to improve the performance of web pages.
1. Improve Page Load Performance: Async and defer help script loading to be non-blocking. This means that the browser won’t wait for them to finish loading before it renders other elements. This results in faster page loads.
2. Control Script Execution: Async and defer allow you to control the order in which scripts are executed. For example, you can choose to load script A before script B, or vice versa.
3. Easier Code Maintenance: If you use async and defer, it is easier to maintain your code since you don’t need to worry about manually managing the order of script loading.
Defer and async are both HTML attributes used to modify the behavior of scripts. The main difference between defer and async is that defer is basically telling the browser to wait until the page has finished parsing to execute the script, while async allows the browser to download and execute the script while the page is being parsed. Defer is most useful when multiple scripts are present on a page and you want them to execute in a certain order, while async is best used when there's only one script and you want it to execute immediately.
-A nested for loop with blocks of synchronous code
-A function call with a return statement inside
-Code executed within an if statement
-A setTimeout() call
-A fetch() request
-A Promise object
1. Improved Performance: Asynchronous code allows multiple tasks to be executed in parallel, meaning that code can be executed more quickly than synchronous code.
2. Better User Experience: Asynchronous code prevents web pages from freezing up, meaning a better user experience because users won't have to wait for responses.
3. Better Server Utilization: Asynchronous code can improve server utilization by allowing multiple requests to be handled in parallel instead of taking up processor time with concurrent requests.
4. Asynchronous Requests: Asynchronous code allows for requests to be handled independently, meaning each request has its own thread, making it possible for applications to handle multiple requests at once.
1. Writing it can be difficult and confusing.
2. You need to pay extra attention to race conditions, which can cause errors on the page or incorrect results.
3. It might block the main UI thread, causing performance issues on the page.
4. Debugging can be difficult, as the code doesn’t always run in the order it’s written.
5. Asynchronous code can be harder to read and understand, making it difficult for others to maintain it.
1. Increased Performance - Asynchronous code allows multiple operations to occur independently, rather than having them block each other as with synchronous code. This allows for better performance when dealing with tasks that take varying lengths of time to finish.
2. Non-Blocking I/O Operations - This is especially useful for applications dealing with I/O operations. Since asynchronous code is non-blocking, it allows an application to make use of other parts while I/O operations are being performed in the background, leading to faster overall performance.
3. Improved Scalability - By utilizing asynchronous code, applications can scale more easily to do more work with fewer resources.
4. Increased Responsiveness - Asynchronous code also helps improve an application’s responsiveness as requests are handled in an event-driven fashion, so user experience is improved.
Synchronous code runs in a linear, top-down fashion. It executes line-by-line, and it will wait for a task to finish before moving on.
Asynchronous code runs in parallel. It doesn’t have to wait for a task to finish before moving on. Asynchronous code can be written using callbacks, promises, async/await, and other similar features.
• Code is easy to write, comprehend, and debug.
• Evaluations are predictable and can be controlled.
• You can plan when the statement executions will take place.
• Long-running processes can block other tasks from executing.
• Possible performance issues, especially when dealing with databases or network calls.
• No way to break away from running processes without termination.
• Non-blocking structure allows multiple tasks to be executed at the same time.
• Faster execution times in comparison to synchronous code.
• Allows complexity in code structure and organization.
• Difficult to comprehend and debug due to callback nesting.
• Longer code with possibility of more bugs due to more complex setups.
• Interruptions to callback chains can cause unpredictable and confusing errors.
1. It is simple to understand and use.
2. Its code is executed one line at a time, making it easier to debug and troubleshoot code.
3. Its execution is guaranteed and guaranteed to run in the order that it was written.
1. It blocks other processes from running until the current process has completed. This can cause the page to freeze until the script is finished.
2. It can lead to long loading times for complex scripts, as all other scripts must wait until the current script is finished before they can run.
1. It allows for non-blocking execution of code; multiple scripts can run at once or in a non-blocking sequence.
2. Asynchronous code can result in faster loading times, as multiple scripts can be executed at once.
3. It can improve responsiveness, as the UI is not blocked while asynchronous scripts are running.
1. It is more complicated to understand and use, as the order of execution is not guaranteed and unpredictable.
2. It can be more difficult to debug and troubleshoot, as issues may arise due to the asynchronous nature of the code.
3. It requires more code to manage multiple async tasks, which can result in more development time.
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