Ajax foundation - HTTP foundation of interview essential knowledge

Dear friends , How do you do , I haven't updated the article for a long time , Today I'll introduce you to a technology , It's called ajax（Asynchronous Javascript And XML）, It is a web development technology for creating interactive web applications .

Popular point theory , You don't have to refresh the page , Submit data to the server through the client , So as to update a part of the web page .（ps： Traditional web pages （ Don't use AJAX） If you need to update the content , You have to reload the entire page ）

Look at the picture ：

Now more and more companies support the separation of front and back-end development , So as a front-end Developer , It is no longer simply limited to making a cutaway , therefore , As a qualified front-end Engineer , Of course, we should master this technology .

Don't talk nonsense , Next, let's learn this technique of holding and holding .

Before learning , You may need to have a little server-side level , What I use here is php. Of course , If you don't understand php It doesn't matter , Only some very simple code is involved here , I won't learn from you ajax Understanding creates stress .

Study ajax Before , We need to know about http Some knowledge of . That's true. , Many beginners are unfamiliar with this knowledge point , But this is a necessary knowledge for many companies to interview . Now follow me , Be familiar with the following knowledge points , You can open about http The gate of knowledge .

First ,http It's the rule that computers communicate over the network , Is a stateless protocol （ It means that after the client sends the request , The server received it , The request was disconnected , Not saved ）

The above is a complete http The process of requesting and responding , Next, let's take a look at these two parts .

Have a look first http Request part ：

（ps： There are many ways to request , But the general use is get and post request ）

Look at the examples , Here is one get request , At the top is the way of request , Address, etc , Then the red part is the request header information , Finally, the request body

Now let's see http The response part of ：

Look at the examples ：

（ps： This example has no response body ）

Then let's look at http The status code of the response , It helps us debug the efficiency and accuracy of the program .

thus ,http There is only so much basic knowledge of , Isn't it rare .

Little knowledge , But keep this in mind , After all, people who will be called engineers in the future , Not too much low（ since high in ...）

I just want to comb some beginners http Just the basics of , Want to know more about , You can read that 《 The illustration HTTP》, Easy to understand （ But I haven't finished reading it completely ）

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Last , I think about it recently , I think it is necessary to build a front-end communication group , You can discuss and exchange front-end technology in it , Share experiences, etc , Jointly improve our front-end development level .