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HTML and JavaScript

HTML and JavaScript. CPSC 222 Ellen Walker Hiram College. Web Servers & Clients. Browser is a web client It sends requests to a server (e.g. cs.hiram.edu) - GET ~walkerel/cs222 Server responds with the text of the file Browser formats the text and displays the file.

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HTML and JavaScript

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  1. HTML and JavaScript CPSC 222 Ellen Walker Hiram College

  2. Web Servers & Clients • Browser is a web client • It sends requests to a server (e.g. cs.hiram.edu) - GET ~walkerel/cs222 • Server responds with the text of the file • Browser formats the text and displays the file. • (Restaurant example)

  3. Getting HTML & JavaScript Examples • Use “view source” on any web site to see what is there! • Choose sites that end in .htm or .html • You will get the html in a separate window • Use “save as” to make your own copy

  4. HTML Commands • Structure • <head>…</head> • Formatting • <h1>This is a major heading </h1> • Links • <a href=http://cs.hiram.edu/~walkerel/cs222> • Scripts (ignored by HTML) • <script> JavaScript goes here </script>

  5. Reading HTML • <env opt1=val1 opt2=val2 …> • Begin environment and set options • </env> • End the environment (in reverse order) • <env1> … <env2> … </env2> … </env1> • Other text (except scripts and comments) • Display directly, ignore tabs and ends of lines

  6. Limitations of HTML • HTML is only for text formatting • It cannot respond to user input • It cannot respond to its environment (e.g. current date) • It cannot do computations

  7. Web Page Computation • On the server • CGI (Common Gateway Interface) • ASP (Active Server Pages - MS) • PHP (Multiplatform command language) • On the client • Java applets: compiled on the server, runs on the client • JavaScript: source code in the web page

  8. Running on the Server • Client requests a page • Server runs a program based on the address • Program generates a web page • Page is delivered to the client, which displays it

  9. Running on the Client • Client requests a page • Server delivers the page • Client interprets (part of) the page as a program and runs the program • Program includes “write” statements to display its result

  10. Why JavaScript? • No compiler needed • No server needed • Clients can read and interpret files on their own computers • Similar structure to Java • Syntax • Object-oriented

  11. Reading JavaScript • Java like statements • Sum = a + b; if (sum > 10) … else … • Input (built-in functions) • alert(“You have to click OK now”); • name = prompt(“What is your name?”) • Input (interaction controls) • <form>… <input type=“button” onclick = “alert(‘you clicked!’)”> … </form>

  12. More JavaScript • Output (directly into page) • document.writeln(“JavaScript worked!”); • Creating and using variables • var query = “How old are you,” + name + ”?” • Defining functions • function name (parameters){ … }

  13. Putting it together <head> <title>test</title> </head> <body> My first java script. <script> name = prompt("what is your name? "); document.writeln("<p>Hello, " + name); </script> </body>

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