Dynamic HTML example to change the appearance of a web page
Display one of over 16 million colours by either;
clicking on one of the samples in the grid on the left,
entering the Red Green Blue values ranging from 0 (low intensity) to 255 (high intensity),
change hue, saturation or lightness by clicking in the square on the right, or click and drag the + or the hue slider.
With a web page there are two types of processing, server side and client side. Processing (in this context) is where data is checked against business rules or the content of the web page is altered to reflect your input. The server is the web server hosting the web site. The client is the computer you are using.
An example of server side processing is where you enter data into a form and then click on a
button. Your input is then examined by the server and either processed or rejected. Server side processing is more secure but has the disadvantage of delays in sending information back and forth from the server.
An example of client side processing is where input is checked for missing values prior to sending to the server. The advantage of client side processing is that time is not wasted waiting for a page to reload to tell you that you have made a mistake or to see the effect of your input. The disadvantage of client side processing is that programming code and business rules are sent to the client and may be read and tampered with by the user.
By using a combination of server and client side processing the advantages of both can be achieved.
On the client side, checking inputed text is one thing, changing the web page appearance is another and for this, Dynamic HTML is used.
By either clicking on one of the samples in the grid or entering the Red Green Blue values above, the sample will change appearance and the Hex value and RGB value will be written to the page (not to a form field like the Red value).
This is also an example of how, not only text data, but visual data (colours) may be entered for storage in a database.
A computer display uses clusters of fixed size dots of red green and blue to represent over 16 million colours by using different intensities of each colour ranging from 0 to 255. With red green and blue all at 0 intensity you get black. With red green and blue all at 255 intensity you get white. This is different from printing where no added colour equals white. In printing the three colours of
are normally used to create all the other colours. In printing a fourth colour of black is often used to save ink. In printing the intensity of each colour can not be altered but the size and spacing of each colour ink drop can be altered and therefore the proportion of each base colour gives rise to the appearance of millions of different colours.
(eXtensible Markup Language)
Ajax is a group of interrelated web development techniques used for creating interactive web applications or rich Internet applications. With Ajax, web applications can retrieve data from the server asynchronously in the background without interfering with the display and behaviour of the existing page.
Below is an example where you can type in the name of an Australian locality and the post code will be retrieved without reloading the page. This trivial example could be accomplished by several other methods but would require pre-loading the almost 16,000 Australian localities and postcodes into the page.
from the menubar, then
key to display the menubar.
in the address bar and make ill advised low level changes.
, click on the
Show advanced settings
link at the bottom, click on the
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