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Keeping context with the hidden element

From: HTML Essential Training

Video: Keeping context with the hidden element

One of the main problems with the way we bpages, work and indeed a problem with the HTTP protocol, is that it's stateless. Every time you send a form response to a server it's a completely new connection and the server has no indication of the context of your session. There is typically no identifying information in the connection to indicate that it's related to another recent connection. To make matters even worse, there could be a number of users using different sessions on the same resource, all from the same IP address or a proxy server.

Keeping context with the hidden element

One of the main problems with the way we bpages, work and indeed a problem with the HTTP protocol, is that it's stateless. Every time you send a form response to a server it's a completely new connection and the server has no indication of the context of your session. There is typically no identifying information in the connection to indicate that it's related to another recent connection. To make matters even worse, there could be a number of users using different sessions on the same resource, all from the same IP address or a proxy server.

Of course, this is why HTTP cookies were invented, but for many uses there's a simpler solution. HTML form supports an invisible element called hidden, sometimes called hidden fields. Let's see how this works. I am going to make a working copy of forms.html and we are going to rename this to forms-working.html. I am going to open this in the text editor here. You'll notice it's using the same forms.css and forms.js that we've been using throughout this chapter. And I'm going to go ahead and open this in our browser as well, and we'll open this with Firefox.

Here's our little form, and you notice that it has a text field, a password field, some checkboxes, and a set of radio buttons. And when I fill it out and press the Big Red Button, you'll notice that we get all of those values. Now we can add to this, and I'm just going to put it down here, and it's not going to go in a paragraph or anything because it doesn't actually display. We can put in some hidden elements. And these are constructed, again, with input. In this case, it's type="hidden," and we can give it a name.

Let's call this one userid and a value="12345," and I'm just going to copy this, give it a few more here. Let's see. We'll have a page and an action and a color, blue, right? Now when I save this and come back over here to our browser--I'm going to reload and I'm just going to press the Big Red Button here-- you'll notice that these hidden fields, we actually get these named/value pairs, and that works the same obviously when you submit it to a CGI script on a server.

And so using these hidden fields, you could keep track of a session. You can keep track of userid. And the other great thing about them as opposed to the cookies, is that these are entirely not persistent, so when this session is done, these are gone and nobody is keeping track of anybody. Of course, if you want to on the other end, you can keep a database. You can have a cookie for your userid. I mean you can use a combination of technologies, but these are a beautiful way of just keeping context of a session between pages in a CGI scripting application.

So, hidden fields are great way to keep context in this session. Unlike cookies, they can be coded right in your HTML and they're not persistent. They can be generated by a script, and they work really well for keeping track of CGI sessions.

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This video is part of

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HTML Essential Training

82 video lessons · 94792 viewers

Bill Weinman
Author

 
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  1. 5m 24s
    1. Welcome
      56s
    2. Using the exercise files
      1m 37s
    3. What you need to know about this course
      2m 51s
  2. 22m 0s
    1. What is HTML?
      4m 12s
    2. Examining the structure of an HTML document
      7m 50s
    3. Understanding tags and containers
      6m 4s
    4. Exploring content models in HTML5
      2m 23s
    5. Looking at obsolete elements
      1m 31s
  3. 27m 19s
    1. Understanding whitespace and comments
      3m 53s
    2. Displaying text with paragraphs
      3m 37s
    3. Applying style
      8m 5s
    4. Using block and inline tags
      6m 34s
    5. Displaying characters with references
      5m 10s
  4. 16m 36s
    1. Exploring the front matter of HTML
      2m 9s
    2. Applying CSS to your document
      3m 59s
    3. Adding scripting elements
      4m 54s
    4. Using the meta tag
      3m 34s
    5. Optimizing your page for search engines
      2m 0s
  5. 24m 59s
    1. Controlling line breaks and spaces
      2m 46s
    2. Exploring phrase elements
      1m 44s
    3. Using font markup elements
      1m 5s
    4. Highlighting text with mark
      1m 29s
    5. Adding headings
      1m 38s
    6. Using quotations and quote marks
      3m 2s
    7. Exploring preformatted text
      1m 45s
    8. Formatting lists
      2m 28s
    9. Forcing text direction
      3m 49s
    10. Suggesting word-break opportunities
      2m 29s
    11. Annotating East Asian languages
      2m 44s
  6. 29m 15s
    1. Introducing CSS
      55s
    2. Understanding CSS placement
      6m 55s
    3. Exploring CSS syntax
      10m 34s
    4. Understanding CSS units of measure
      3m 3s
    5. Some CSS examples
      7m 48s
  7. 22m 5s
    1. Using images
      4m 13s
    2. Flowing text around an image
      4m 55s
    3. Breaking lines around an image
      3m 3s
    4. Aligning images
      5m 25s
    5. Mapping links in an image
      4m 29s
  8. 22m 28s
    1. Understanding URLs
      2m 41s
    2. Working with hyperlinks
      3m 28s
    3. Using relative URLs
      4m 20s
    4. Specifying a base URL
      2m 19s
    5. Linking within a page
      4m 12s
    6. Using image links
      5m 28s
  9. 17m 2s
    1. Exploring list types
      3m 52s
    2. List elements in depth
      7m 44s
    3. Using text menus with unordered lists
      5m 26s
  10. 15m 30s
    1. Introduction to HTML semantics
      4m 9s
    2. Exploring an example
      4m 56s
    3. Marking up figures and illustrations
      2m 33s
    4. Creating collapsible details
      3m 52s
  11. 11m 18s
    1. Embedding audio
      5m 19s
    2. Embedding video
      5m 59s
  12. 11m 53s
    1. Creating ad-hoc Document Object Model (DOM) data with the data-* attribute
      4m 53s
    2. Displaying relative values with meter
      2m 57s
    3. Creating dynamic progress indicators
      4m 3s
  13. 4m 49s
    1. Overview of HTML5 microdata
      1m 8s
    2. Exploring an example with microdata
      3m 41s
  14. 7m 3s
    1. Understanding outlines
      52s
    2. A demonstration of outlining
      6m 11s
  15. 13m 1s
    1. Table basics
      7m 29s
    2. Exploring the semantic parts of a table
      2m 32s
    3. Grouping columns
      3m 0s
  16. 9m 55s
    1. Frames overview
      54s
    2. Using traditional frames
      4m 26s
    3. Exploring inline frames using iframe
      2m 7s
    4. Simulating frames with CSS
      2m 28s
  17. 53m 7s
    1. Introducing forms
      10m 24s
    2. Using text elements
      10m 12s
    3. Using checkboxes and radio buttons
      2m 37s
    4. Creating selection lists and dropdown lists
      5m 14s
    5. Submit and button elements
      8m 48s
    6. Using an image as a submit button
      2m 15s
    7. Keeping context with the hidden element
      3m 0s
    8. Setting tab order
      2m 7s
    9. Preloading an autocomplete list using the datalist feature
      5m 26s
    10. Displaying results with output
      3m 4s
  18. 19m 47s
    1. Touring a complete site
      2m 14s
    2. Touring the HTML
      8m 44s
    3. Touring the CSS
      8m 49s
  19. 29s
    1. Goodbye
      29s

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