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This alternative can cut down significantly on server demands
and network traffic, but it requires that processing instructions be
conveyed to a browser so that it knows how to process some of the
data before transmitting anything to the server. JavaScript is one
common tool for writing such instructions within an HTML Web
page. JavaScript provides a mechanism for writing various types of
computer programs within a Web page to allow the browser to han
dle some processing chores. When a Web page instructs the browser
on how to do some processing, it has initiated client-side process-
ing . As with many parts of computing, clientside processing capa
bilities have both advantages and disadvantages. The major advan
tage? JavaScript processing allows local processing. The major
disadvantage? JavaScript processing allows local processing.
To explain, local processing with JavaScript allows fast re
sponse to user interactions, keeps network traffic to a minimum,
and places little burden on servers. All of these capabilities offer
significant benefits. Local processing with JavaScript also means,
however, that a user may run unknown programs with little or no
supervision. This may or may not cause problems with your com
puter. In principle, JavaScript is designed to have only a limited
collection of capabilities, and the processing possibilities are not
supposed to harm your local computer. For example, JavaScript
cannot open files on your local computer, erase your files, send
email under your name, or otherwise interact with your local
computer without your explicit permission. On the other hand,
because JavaScript allows users to run unknown programs and be
cause computer software sometimes contains errors, some people
worry that JavaScript programs might exploit weaknesses in a
browser with detrimental results. When a user downloads a Web
page, the user may or may not even know if the page contains a
JavaScript program, and the user rarely will have reviewed the
program ahead of time to determine that it functions in a desirable
manner. For this reason, some computer users set their browsers
so that JavaScript programs cannot be run. Even though most
JavaScript programs work nicely, people using Web pages cannot
be certain who wrote the JavaScript programs, and thus cannot
know what these programs actually do. Thus, although running
JavaScript may have potential advantages, JavaScript programs
also may open the user to possible risks, and skeptics are not will
ing to take chances.
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