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JavaScript and JQuery: Interactive Front-End Web Development by Jon Duckett

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13

FORM ENHANCEMENT & VALIDATION

Forms allow you to collect information from visitors, and JavaScript can help you get the right information from them.

Since JavaScript was created, it has been used to enhance and validate forms. Enhancements make forms easier to use. Validation checks whether the user has provided the right information before submitting the form (if not, it provides feedback to the user). This chapter is divided into the following three sections:

FORM ENHANCEMENT

This section features many examples of form enhancement. Each one introduces the different properties and methods you can use when working with form elements.

HTML5 FORM ELEMENTS

HTML5 contains validation features that do not use JavaScript. This section addresses ways in which you can offer validation to old and new browsers in a consistent way.

FORM VALIDATION

The final, and longest, example in the book shows a script that validates (and enhances) the registration form that you can see on the right-hand page. It has over 250 lines of code.

The first section of this chapter also drops jQuery in favor of plain JavaScript, because you should not always rely upon jQuery (especially for scripts that use little of its functionality).

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HELPER FUNCTIONS

The first section of this chapter uses plain JavaScript, no jQuery. We will create our own JavaScript file to handle cross-browser issues, it will contain one ...

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