When using a web server as a back-end to an HTML page, for example filling in a form, the result from the back-end can be
- “Redirect to a new page”.
- A stream of HTML. This is an HTML document where the “boilerplate” or constant data, is intermixed with the variable data included inline. The HTML is displayed, and replaces the previous page.
- A stream of data containing data such as changed fields. The requesting page can use this stream to update its page.
Sending a complete HTML document
Using a python back-end program I can write an entire (and complete) HTML document.
#!/usr/bin/python3
import cgitb
import cgi
cgitb.enable()
print("Content-Type: application/json")
print("ColinHeader: Value")
print("ColinHeader2: Value")
# indicate end of headers
print()
# now the html page
print("<!doctype html>")
print('"<html lang="en">')
print("<head>"
print("<body>")
print('<form id="target" action="cgi-bin/first.py" enctype="multipart/form-data" >')
print('<label for="email">Enter your email: </label>')print('<input id=email name="email" value="test@example.com" title="colins email address">')print('<label for="password">Enter your pw: </label>')print('<input id=password name="password" value="pw">')print('<input type="submit">')print("</form>")
print("</body>")
print("</html>")
Where
- print(‘<label for=”email”>Enter your email: </label>’)is constant text.
- print(‘<input id=email name=”email” value=”test@example.com” title=”colins email address”>’)is the variable data putting text@example.com into the field.
- print(‘<label for=”password”>Enter your pw: </label>’)is constant text.
- print(‘<input id=password name=”password” value=”pw”>’)is variable text, putting pw into the field.
This is a terrible way of doing it. Presentation (red text) is mixed up with data (green text). This was a no-no about 40 years ago! You might have several similar pages, and any updates would have to be made to all pages. Using pages in national different languages is hard to implement; you need to have a multiple program, one for each language.
ColinPaice 
One thought on “Updating a web page from a server – sending a complete HTML document.”