Cause analysis and solution of too laggy page of [test interview questions]

Recent market conditions , Many partners have the intention of passive job hopping , Recently, the editor will mainly update some relevant interview questions , I hope that helps .

In fact, many interviewers ask some questions , Mainly want to examine the candidates' logical thinking ability and expression ability . Novice testers are not experienced enough , It is often easy to miss some key points , Therefore, it is suggested that you should be well prepared before the interview .

The specific operation is actually to brush the surface more , When encountering some common problems , Don't worry about looking for the answer first , But first think about how you would answer .

Just imagine , If the interviewer happens to ask the question you reviewed , Can it help you improve your interview success rate ？

Tip： If you encounter a prepared problem , Don't rush to finish all the answers at once , Show the process of your thinking , On the one hand, don't let the interviewer feel like you recite the topic , I don't have my own understanding ; On the other hand, you can also want to see if there are any missing points .

Don't talk much , The reason analysis and solution of the too laggy page are as follows ：

The reason a ：http Too many requests

solve ： Reduce http Number of requests .

①　 Picture map ： Integrate multiple pictures into one picture , Locate hyperlinks by location .
②　CSS
Sprites Merge pictures , By designation CSS Of backgroud-image and backgroud-position To display elements .
③　 Merge JS Scripts and CSS Style sheets .
④　 External use JS and CSS file .

Reason two ： Receiving data takes too long , If the download resources are too large

solve ： Yes HTTP The transmission is compressed .

That is to say js,css、 Pictures and other resources have been compressed , stay HTTP Re compression during transmission .

The client can use the Accept-Encoding Header to declare the compression method supported by the browser , Server through Content-Encoding To enable compression , Configure compressed file types , Compression way .gzip Using lossless compression , The compression effect is the best , It has become the most widely used 、 The most data compression formats supported by browsers .

Reason three ：JavaScript The script is too large , Blocking page loading

solve ： take JavaScript Put the script in front of the label .

script No, async and defer when ,JS The file will be executed immediately after downloading . In this case ,script Putting it at the top will block the page rendering , When the network speed is slow, it will lead to “ hang ”, Don't continue rendering the page until the script is downloaded .

therefore ,script Put it at the bottom to make the page appear as soon as possible .
https://blog.csdn.net/zhouziyu2011/article/details/71330739

Reason four ：CSS、JavaScript、 Pictures need to be loaded repeatedly

solve ： Static resources are placed on a static domain name , Reduce the burden of repeatedly downloading static resources .

Reason five ：cookie influence

solve ： Reduce cookie Influence .

①　 Remove unnecessary cookie, If the web page doesn't need to cookie It's totally forbidden .
②　 take cookie Minimize the size of ： Reduce HTTP Size of request message , Improve response time .
③　 Set the appropriate expiration time ：cookie The information will be stored on the hard disk , Even if the browser exits cookie There will be , as long as cookie Not cleared and still within the expiration time , The cookie It will be sent to the server when accessing the corresponding domain name .
④　 By using different domain Reduce cookie Use ：cookie When accessing the resources under the corresponding domain name, you will pass HTTP The request is sent to the server , But when accessing some resources , Such as js,css And pictures , Most of the time cookie It's redundant , You can use different domain To store these static resources , In this way, when accessing these resources, no extra cookie, So as to improve the response speed .

Reason six ： Too many web resources

solve ： Use CDN Deploy the network to improve download speed , You can go through free CDN Suppliers to distribute web resources .

reason ：DNS Parsing speed

DNS Resolution is from domain name to IP Parsing .DNS Parsing includes the number of iterations and the time spent on each parsing , The product of the two is DNS The total time spent parsing . Many people ignore DNS Analytic factors , In fact, it is also very important for website parsing speed . You can replace the one with low delay DNS The server .