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#REDIRECT [[Dynamic web page#Client-side scripting]]
'''Client-side scripting''' generally refers to the class of [[computer program]]s on the [[World Wide Web|web]] that are [[Execution (computers)|executed]] ''[[client-side]]'', by the user's [[web browser]], instead of ''[[server-side]]'' (on the [[web server]]). This type of [[computer programming]] is an important part of the [[Dynamic HTML]] (DHTML) concept, enabling [[web page]]s to be [[Script (computer programming)|scripted]]; that is, to have different and changing content depending on user [[input]], environmental conditions (such as the time of day), or other variables.
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Web authors write [[client-side]] scripts in languages such as [[JavaScript]] ([[Client-side JavaScript]]) or [[VBScript]], which are based on several standards:
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*[[HTML scripting]]
*[[HTTP]]
*[[Document Object Model]]
Client-side scripts are often embedded within an [[HTML]] document, but they may also be contained in a separate [[Computer file|file]], which is referenced by the document (or documents) that use it. Upon request, the necessary files are sent to the user's computer by the [[web server]] (or servers) on which they reside. The user's [[web browser]] [[Execution (computers)|executes]] the script, then displays the document, including any visible output from the script. Client-side scripts may also contain instructions for the browser to follow if the user interacts with the document in a certain way, e.g., clicks a certain button. These instructions can be followed without further communication with the server, though they may require such communication.
By viewing the file that contains the script, users may be able to see its [[source code]]. Many web authors learn how to write client-side scripts partly by examining the source code for other authors' scripts.
In contrast, [[server-side scripting|server-side scripts]], written in languages such as [[Perl]] and [[PHP]], are executed by the web server when the user requests a document. They produce output in a format understandable by web browsers (usually HTML), which is then sent to the user's computer. The user cannot see the script's source code (unless the author publishes the code separately), and may not even be aware that a script was executed. The documents produced by server-side scripts may, of course, contain client-side scripts.
uthor to that is not supported by the web browsers used by a majority of his or her audience.fortunately, even languages that are supported by a wide variety of browsers may not be implemented in precisely the same way across all browsers and operating systems. Authors are well-advised to review the behavior of their client-side scripts on a variety of [[Platform (computing)|platforms]] before they put them into use.
[[Category:Scripting languages]]
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