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Building interactive jQuery validation

From: Validating and Processing Forms with JavaScript and PHP

Video: Building interactive jQuery validation

In the previous movie, we created validation when the user submits the form. Now I'm going to show you how to handle more interactive validation. This time we're going to check for validation when the user exits a field and has a placeholder attribute. So I'm going to come right here and I'm going to do the dollar sign again. And I'm going to type in input. And then use the type selector which are these brackets and type in place holder that way we'll look for fields that are input fields and also have a place holder. And then we'll attach the blur method. The blur method will happen when somebody exits a field. So this will execute a function.

Building interactive jQuery validation

In the previous movie, we created validation when the user submits the form. Now I'm going to show you how to handle more interactive validation. This time we're going to check for validation when the user exits a field and has a placeholder attribute. So I'm going to come right here and I'm going to do the dollar sign again. And I'm going to type in input. And then use the type selector which are these brackets and type in place holder that way we'll look for fields that are input fields and also have a place holder. And then we'll attach the blur method. The blur method will happen when somebody exits a field. So this will execute a function.

This is going to be a function literal, or a function with no name. And we're going to do something in here. So, what I'm going to do is, remove the current errors that are on the page. Now, I'm going to create a set of variables that's going to keep track of things. First, a variable to receive the pattern from the pattern attribute in the form. Then another variable for the place holder. Finally, we'll do one to check whether the value of the field matches our pattern. Most of this is still going to be regular JavaScript, so we'll check for the value of the current field, and then use the regular JavaScript search method.

We'll see if it's a positive number. If it's a negative number, then the pattern hasn't been matched, so we'll check for that in an if statement. So if the pattern is not valid, then I'm going to execute some code right here. And that code will be to insert some HTML displaying the error right after the current field, so sort of like what we did up here. So I'll copy that code and change this text. Now, if it's not valid, we can also do one more thing. I'm going to move the insertion point to the field that doesn't match the current pattern.

Let's also add some comments. Now I'm going to Save this and I'll go back into my form. I'll refresh the page and I'll try to type something that doesn't match the pattern. Notice that its telling me that the entry does not match the expected pattern. And it reads the pattern value. And it won't let me go to another field until the pattern's correct. Same thing with the telephone number. Once again, our script is a lot shorter when we use the jquery library. As a byproduct, it's also more compatible. For example, older browsers support HTML attributes like pattern and placeholder inconsistently.

Although it has a lot of other benefits, adding a library to your projects is going to increase the file size of your page's download. So, when using Jquery, you'll have to weigh whether the added features warrant the slightly larger download size for your users.

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This video is part of

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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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