URL(Universal Resource Locator)
Hypertext is text with links to other text, click on which takes you somewhere else. URL provides names for web content.
For example, http://host.company.com:80/a/b/c.html?user=Alice&year=2008#p2
:
- Scheme(http:): identifies protocol used to fetch the content.
- Host name(//host.company.com): name of a machine to connect to.
- Server’s port number(80): allows multiple servers to run on the same mathine.
- Hierarchical portion(/a/b/c.html): used by server to find content.
- Query parameters(?user=Alice&year=2008): provides additional parameters.
- Fragment(#p2): Have browser scroll page to fragment.
Schemes
There are ~350 schemes:
- http: is the most common scheme; it meand use the HTTP protocol.
- https: is similar to http, except that it uses SSL encryption(加密).
- file: means read a file from the local disk.
- websocket: means create a TCP connection.
- mailto: means open an email program composing a message.
- …
Hierarchical portion
URL is passed to the web server for interpretation. One way is pass the name of a static HTML file, the other way is pass the name of a program that will generate the HTML content.
Web server is programmed with routing information. It can map hierarchical position to functionto be performed and possibly the function’s parameters.
Use of URLs
- Load a page: type the URL into your browser.
- Load a image:
<img src="...">
- Load a stylesheet:
<link rel="stylesheet" type="text/css" href="...">
- Embedded a page:
<iframe src="http://www.google.com">
JavaScript Basics
What is JavaScript
- …high-level, dynamic, untyped and interpreted programming language.
- …prototype-based with first-class functions,…
- …supporting object-oriented, imperative and functional programming.
- … has an API for working with text, arrays, dates and regylar expressions.
- 本文作者: 夏花
- 本文链接: http://xiahua19.github.io/2022/08/10/cs142-2-URL-and-JavaScript/
- 版权声明: 本博客所有文章除特别声明外,均采用 MIT 许可协议。转载请注明出处!