TAILIEUCHUNG - JavaScript Bible, Gold Edition part 146

JavaScript Bible, Gold Edition part 146. This book will bring programmers and non-technical professionals, including casual programmers and scripters, painlessly up to speed on all aspects of mastering JavaScript. Key topics include programming fundamentals, JavaScript language elements and how to use them effectively, and how to easily and efficiently add powerful new functionality to HTML documents and Java applets. | 1298 Part V Putting JavaScript to Work Note The dynamic calendar in Listing 49-2 assumes that the browser treats like-named text boxes in a form as an array of fields. While this is true in all versions of NN IE3 does not follow this behavior. To accommodate this anomaly you must modify the script to assign unique names to each field with an index number as part of the name and use the eval function to assist looping through the fields to populate them. On the CD-ROM is Listing 49-2b which is a cross-compatible version of the dynamic calendar. Application A Lookup Table 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 less than 56 Kbps how large an image file would you tolerate downloading Whatever that limit may be anywhere from 10 to 35K depending on your patience is what your database size limit should be. For .

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