JavaScript - Single Field Validation

JavaScript provides an easy way to validate single fields on an HTML form. The Guest Book done earlier in this course is an example of using JavaScripts.

JavaScript provides an easy way to do the following types of validation:

test for Null
integer range checking
Min or Max text length checking
special character checks - like EMAIL addresses
specific list of valid values

ADVANTAGES:

Integrates nicely with HTML form "Input Type" components like text, checkbox, and button.
Extends built in functionality of HTML components while maintaining the same look and feel.
Script is embedded in same page that is used to collect the data.
Simple to program and understand.

DISADVANTAGES:

Difficult to validate each field as the data is entered. "onBlur" event has problems with this.
No events to capture each keystroke for extremely tight validation.
Limited to HTML components.
Common functions must be replicated on each page.

See the following examples to see how this works.

JAVAScript Example 1 Demonstrates checking for required and optional fields, min and max lengths, and a special character check.
JAVAScript Example 2 Demonstrates alpha character checks and numeric checks.

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JAVAScript Example 1	Demonstrates checking for required and optional fields, min and max lengths, and a special character check.
JAVAScript Example 2	Demonstrates alpha character checks and numeric checks.