AJAX and PHP

Chapter 6
visible, we need to scroll in the region in order to make that result visible. In order to implement
this, we keep minimum and maximum positions of the results that are currently visible. It's as if
we had a window that moves through the results according to the arrows' movements and the
current selected result.
The selectRange and autocompleteKeyword functions do the trick for the type-ahead look by
autocompleting the current keyword with the rest of the missing letters up to the first suggestion.
The part that is missing is added as highlighted text to the current keyword. The select() method
selects all the text, and hence selecting only a part of a text is not possible. In order to do this,
Internet Explorer offers one solution while Mozilla / Firefox offers another one. It is not for the
first time that issues are not the same in all browsers, so we have to take each case and solve it
separately. In Firefox, issues are simple because there is just one function that does all the work
for us—setSelectionRange. This function takes two parameters—the start position of the
selection and the length of the selection. In Internet Explorer, we have to use the TextRange object
in order to achieve the same goal. Let us take a closer look at it because it might be useful for us in
the future and for this, we need to know what it can do.
The TextRange object can carry out tasks such as searching or selecting text. Text ranges let you
pick out characters, words, and sentences from the text. Each of these three is a logical unit of the
object. In order to use such an object you have to follow these steps:
• Create the text range
• Apply a method to the selected text
You can copy the text, search in the text, and select a part of the text, as in our case.
To create such an object you can call the createTextRange method on a body, textarea, or
button element.
Each object has a start and an end position defining the scope of the text. When you create a new
text range, the start and end positions contain the entire content by default. To modify the scope of
the text range we can use the move, moveStart, and moveEnd functions. Each of them takes two
parameters—the first parameter specifies the logical unit and the second one the number of units
to move. The result contains the numbers of units moved. The select method makes the selection
equal to the current object. In order to have a complete view of its capabilities check the following
link on MSDN: http://msdn.microsoft.com/library/default.asp?url=/workshop/
author/dyncontent/textrange.asp.
After receiving the suggestions and inserting them into the page, we need to autocomplete the
keyword with the value of the first suggestion. This is accomplished by using the selectRange
function described above.
For the error-handling part, we use the displayError function that displays an alert with the error
message as parameter.
OK, now we have seen how it goes for the client side of the application. Let's check the server side.
For the server side, things are very simple. The suggest.php file retrieves the parameter passed by
the client and that represents the searched for keyword. Then it calls a method of the Suggest class
187
www.it-ebooks.info