JavaScript - Inter-Field Validation

JavaScript is limited in what it can do for inter-dependent fields. It can provide some limited functions such as controlling text entry based on some other selection. However, it can not be used to do things like dynamically changing choices from a selection list.

ADVANTAGES:

Straight forward technique for a JavaScript knowledgeable developer.
Integrates well with HTML forms.

DISADVANTAGES:

Difficult to build general purpose functions.
Logic is hard-coded to Form's components.
Limited functionality for control of components.

See the following examples to see how this works.

Example 1 Demonstrates local vs long distance phone number selection.
Example 2 T-Shirt Order Example. Demonstrates how an entered field is used to calculate other fields.

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Example 1	Demonstrates local vs long distance phone number selection.
Example 2	T-Shirt Order Example. Demonstrates how an entered field is used to calculate other fields.