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Write AJAX applications in raw JavaScript using HttpRequest and related technologies.
No pre-written libraries or frameworks are used.
Frequency of use:
medium low
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Developing AJAX-style applications is hard. It requires that you know JavaScript,
DOM, CSS, HTML, XML, SOAP,
and related technologies. In addition, you are expected to have a good grasp of the
many subtle, and not-so-subtle, cross-browser differences.
Fortunately, numerous robust libraries are available, including
commercial, open source, Microsoft AJAX, and others. This allows for fast and effective AJAX development. As
these libraries mature, the frequency at which developers use low level
Javascript will decrease over time.
In the example below, AJAX has been
implemented at Level 1, that is, AJAX functionality has been implemented in raw JavaScript without
the use of a pre-built AJAX library.
In this example, the user selects a training class using three cascading
dropdowns. First the course is selected, then the city, and finally the date.
Notice how the selection of one dropdown populates the next
dropdown and moves focus forward. No postbacks are issued, which
is why you see no page flicker.
This cascading selection process has been AJAXified
without the help of any external AJAX library. Items in the dropdown lists are
retrieved asynchronously from the server using an HttpRequest object that issues
HTTP GETs against a standard .aspx web page.
Alternatively, the HttpRequest object could have issued SOAP requests against a
web service, but this would have been more complex because it requires knowledge
of how SOAP messages are built.
Example: Select a training class
Choose a course:
Choose a city:
Choose a date:
[No class selected yet]
Click here to view the source code.