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Validating and Processing Forms with JavaScript and PHP

Using the selectedIndex property


From:

Validating and Processing Forms with JavaScript and PHP

with Ray Villalobos

Video: Using the selectedIndex property

Just about all the text fields in an HTML form are input fields. The exceptions are the text area field, which is really just like a text field, and also the select field. The select field is quite another beast, so I wanted to cover how to handle onchange events on select fields. Select fields have a special and very useful property called the selectedIndex property, which shows you the option that a user has selected from its list. So, let's take a look at this form, which we're going to be working on in this movie.
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  1. 3m 36s
    1. Welcome
      1m 9s
    2. What you should know
      1m 2s
    3. Using the exercise files
      1m 25s
  2. 12m 50s
    1. Understanding forms
      2m 2s
    2. Working with form fields
      7m 4s
    3. Using the form tag
      3m 44s
  3. 19m 23s
    1. Using input validation
      2m 10s
    2. Adding required fields and placeholders
      1m 31s
    3. Constraining numeric and date fields
      2m 32s
    4. Accepting multiple entries
      1m 41s
    5. Limiting uploads by MIME types
      2m 35s
    6. Assisting text input with a datalist
      1m 55s
    7. Constraining with regular expression patterns
      6m 59s
  4. 42m 13s
    1. Accessing forms
      3m 57s
    2. Looking up form elements
      3m 35s
    3. Handling focus changes
      2m 47s
    4. Detecting the onchange event
      4m 31s
    5. Using the selectedIndex property
      2m 30s
    6. Dynamic validation with regular expressions
      7m 0s
    7. Creating a generic input validation function
      4m 31s
    8. Validating in older browsers with Modernizr
      7m 32s
    9. Interrupting form submission with onsubmit
      5m 50s
  5. 15m 20s
    1. Understanding jQuery
      3m 47s
    2. Validating on submit with jQuery
      3m 45s
    3. Building interactive jQuery validation
      2m 34s
    4. Using the jQuery Validation plugin
      5m 14s
  6. 32m 57s
    1. Communicating with PHP servers
      2m 27s
    2. Retrieving data from superglobals
      8m 18s
    3. Using server-side validation
      4m 59s
    4. Adding in-page validation
      5m 22s
    5. Mirroring input data back to the user
      7m 46s
    6. Sanitizing form input
      4m 5s
  7. 43m 29s
    1. Mailing form data
      8m 28s
    2. Understanding file uploads
      3m 1s
    3. Uploading files
      9m 20s
    4. Processing form data with AJAX
      8m 14s
    5. Preparing your database
      5m 50s
    6. Pushing data
      8m 36s
  8. 1m 17s
    1. Next steps
      1m 17s

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Validating and Processing Forms with JavaScript and PHP
2h 51m Intermediate Apr 23, 2013

Viewers: in countries Watching now:

Validating web forms is a critical skill for any web developer, ensuring that the data that's submitted is complete, accurate, and nonmalicious before it's sent off to the server. Join author Ray Villalobos in this course as he shows how to validate input from site visitors with HTML5, JavaScript, and jQuery and then process the data with PHP. Plus, learn how to email form data and save it in a MySQL database so that it's ready for other applications.

Topics include:
  • Understanding forms
  • Adding required fields and placeholders
  • Accepting multiple entries
  • Limiting uploads
  • Handling focus changes
  • Validating with regular expressions
  • Working with older browsers
  • Building jQuery validation
  • Using server-side validation
  • Sanitizing form input
  • Uploading files
  • Sending form data to a database
Subjects:
Developer Web Web Design Databases Web Development
Software:
JavaScript PHP
Author:
Ray Villalobos

Using the selectedIndex property

Just about all the text fields in an HTML form are input fields. The exceptions are the text area field, which is really just like a text field, and also the select field. The select field is quite another beast, so I wanted to cover how to handle onchange events on select fields. Select fields have a special and very useful property called the selectedIndex property, which shows you the option that a user has selected from its list. So, let's take a look at this form, which we're going to be working on in this movie.

This form just has a single field, and it's a pop up field with a list of some websites. If you take a look at the code, you'll see that the value field for each of those is an actual site. So what I'm going to do is, after the form field, I'm going to add a script tag. And on that script tag, I'm going to target the form. And our field is called reference, so I'll target that. And I'll add an onchange event handler. That's going to be a function literal, means just a function with no name. And inside that, I'm going to create a variable, called id, that is going to hold the value of the selected index field for that form. So I'll target the document, form, and then the reference, element. And I want to target the selectedIndex property of that field. So I'll store the selection from the user into this variable called id. Now once I have that, I can get the value of the selected element, and put that in another variable.

So, I'll create another variable called url, and that's going to be pretty much the same thing, document, target the form, then the reference variable. And I'll pass it along the id, that's the variable we just created. And I need the value of that id. So, my URL is going to be the value of the item that the user has selected. Now after that, I'll set the location of the window. So I'll do Window > Location. And set the href, or the URL of the current window, to that URL that we received from the pop up list. So, let me go ahead and save this, and I'll go back into my form, and I'll refresh.

You'll see that whenever I chose one of these elements, it's actually going to go to that website. So, although the onchange event still triggers in the same way for select and input fields, getting information about a select field is a bit different. The selectedIndex property helps you access the option that has been chosen by the user.

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