20.4. Extracting Query
Parameters of an URL
In
this section, we will demonstrate how to extract query parameters of
an URL using some of the functions that we learned before.
Before
extracting query parameters, we have to obtain the query string of
the URL first. This can be done using the getQuery()
function that we learned
in the last section.
After
extracting the query string from the URL, you can use the elements()
and elementAt()
functions of the String standard library to extract the query
parameters. For example, let's say the query string obtained
is "q1=Hello&q2=Welcome%20to%20our%20WMLScript%20tutorial".
We use the following example script to extract the parameters and
assign their values to a variable
named message, whose
value can be displayed in a WML card if you want to do so:
var
queryString =
"q1=Hello&q2=Welcome%20to%20our%20WMLScript%20tutorial"; var
paraTemp = ""; var message = ""; for (var
i=0; i<String.elements(queryString, "&");
i++){ paraTemp = String.elementAt(queryString, i,
"&"); message += "The value of the " +
String.elementAt(paraTemp, 0, "=") + " parameter is '"
+ String.elementAt(paraTemp, 1, "=") + "'. "; }
After
executing the above script, the message
variable contains the string value "The value of the q1
parameter is 'Hello'. The value of the q2 parameter is
'Welcome%20to%20our%20WMLScript%20tutorial'. ".
Here
is a brief description of what we do in the above WMLScript example.
First, we use the & character as the separator to divide the
query string into two substrings "q1=Hello" and
"q2=Welcome%20to%20our%20WMLScript%20tutorial".
Next,
we divide each of the substrings into two parts using the = character
as the separator. For example, we divide "q1=Hello" into
"q1" and "Hello".
Finally,
we output the parameter names and parameter values to the message
variable.
As
you can see above, the value the q2
parameter is in the escaped form. The unescapeString()
function can help us
unescape the hexadecimal sequence:
message
= URL.unescapeString(message);
After
executing the above line of script, the message
variable contains the string value "The value of the q1
parameter is 'Hello'. The value of the q2 parameter is 'Welcome to
our WMLScript tutorial'. ".
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