How the web works provides a simplified view of what happens when you view a webpage in a web browser on your computer or phone.
This theory is not essential to writing web code in the short term, but before long you'll really start to benefit from understanding what's happening in the background.
Computers connected to the web are called clients and servers . A simplified diagram of how they interact might look like this:
The client and server we've described above don't tell the whole story. There are many other parts involved, and we'll describe them below.
For now, let's imagine that the web is a road. On one end of the road is the client, which is like your house. On the other end of the road is the server, which is a shop you want to buy something from.
In addition to the client and the server, we also need to say hello to:
When you type a web address into your browser (for our analogy that's like walking to the shop):
When browsers send requests to servers for HTML files, those HTML files often contain
<link>
elements referencing external
CSS
stylesheets and
<script>
elements referencing external
JavaScript
scripts. It’s important to know the order in which those files are
parsed by the browser
as the browser loads the page:
<link>
-element references to external CSS stylesheets and any
<script>
-element references to scripts.
<link>
elements, and any JavaScript files it has found from
<script>
elements, and from those, then parses the CSS and JavaScript.
Real web addresses aren't the nice, memorable strings you type into your address bar to find your favorite websites. They are special numbers that look like this:
63.245.215.20
.
This is called an IP 地址 , and it represents a unique location on the web. However, it's not very easy to remember, is it? That's why Domain Name Servers were invented. These are special servers that match up a web address you type into your browser (like "mozilla.org") to the website's real (IP) address.
Websites can be reached directly via their IP addresses. You can find the IP address of a website by typing its domain into a tool like IP Checker .
Earlier we used the term "packets" to describe the format in which the data is sent from server to client. What do we mean here? Basically, when data is sent across the web, it is sent in thousands of small chunks. There are multiple reasons why data is sent in small packets. They are sometimes dropped or corrupted, and it's easier to replace small chunks when this happens. Additionally, the packets can be routed along different paths, making the exchange faster and allowing many different users to download the same website at the same time. If each website was sent as a single big chunk, only one user could download it at a time, which obviously would make the web very inefficient and not much fun to use.
Street photo: Street composing , by kevin digga .
最后修改： , 由 MDN 贡献者