JavaScript® Bible, Sixth Edition

Chapter 50. Application: A Lookup Table

IN THIS CHAPTER

• Serverless data collection lookup

• Data-entry validation

One of the first ideas that intrigued me about JavaScript was the notion of delivering CGI-like functionality along with an HTML document. On the Web, numerous, small data collections currently require CGI scripting and a back-end database engine to drive them. Of course, not everyone who has information to share has access to the server environment (or the expertise) to implement such a solution. JavaScript provides that power.

A Serverless Database

Before you get too carried away with the idea of letting JavaScript take the place of your SQL database, you need to recognize several limitations that prevent JavaScript from being a universal solution. First, any database that you embed into an HTML document is read-only. Although you can script an interface and lookup routines for the user, no provisions are available for writing revised information back to the server, if that is your intention.

A second consideration is the size of the data collection. Unlike databases residing on servers, the entire JavaScript database (or subset you define for inclusion into a single HTML document) must be downloaded to the user's browser before the user can work with the data. As a point of reference, think about image files. At 56.6 Kbps through a dial-up connection, how large an image file would you tolerate downloading? Granted, a vast majority of users now have broadband access of some ...