| 8 |
For Loop (Loop) |
| 8.1 |
A For loop will loop over a single operation or a block of operations contained within a set of curly braces ({}). The loop takes three arguments with each one being optional.
Initial Value
Condition to continue the loop
Operation to take at end of iteration.
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| 8.2 |
The initial value is usually set as a normal variable set. This will
create a variable and give it an initial value. This is a global variable
and care must be taken so it does not affect other variables or pieces
of code. |
| 8.3 |
The condition to continue the loop takes a standard comparison statement
and checks if it is true. If it is, then the loop will go again. This
check is done at the beginning of each loop iteration. |
| 8.4 |
The operation to take at the end of the loop iteration is a standard assignment that will occur when a loop iteration is done but before the check to continue is performed. |
| 8.5 |
A standard For loop may look like this. The variable i is set to an
initial value of 1. At the end of the loop, i is incremented and then
it is checked to see if it is less then or equal to 10. If it is, then
the loop will run another iteration.
<CFSCRIPT>
For (i=1;i LTE 10; i=i+1)
writeoutput(i&' ');
</CFSCRIPT>
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| 8.5.1 |
The LTE syntax is used due to the order of operation. If the operation was LT 10, then there would only be 9 iterations of the loop. If the EQ syntax was used, it would fail to run in the first place.
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| 8.5.2 |
The syntax i=i+1 is used because ColdFusion does not have an incrementation syntax of i++. The IncrementValue() function could be used, but is both slow and is wasted here. |
| 8.6 |
The variable set and the end operation do not have to be numeric in
nature. This example shows how to set the initial value to a character,
increment the character and check it to see if the loop should end. It
will output the letters M, N and O seperated by a space.
<CFSCRIPT>
For (i="M";i NEQ "P"; i=Chr(Asc(i)+1))
writeoutput(i&' ');
</CFSCRIPT>
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| 8.7 |
A For loop can also be used to loop through a query object. This For loop will loop through a query and output each row of column record to the browser. (This example is provided to show that you can use CFSCRIPT to loop over a query. If this is the only operation you are doing, a CFLOOP or a CFOUTPUT would be perfered).
<CFSCRIPT>
For (i=1;i LTE Queryname.Recordcount; i=i+1)
writeoutput(Queryname.Record[i]&'<BR>');
</CFSCRIPT>
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| 8.8 |
A For loop can also be used to loop through a list. This For loop will loop through a list and output each item.
<CFSCRIPT>
For (i=1;i LTE ListLen(list); i=i+1)
writeoutput(ListGetAt(list, i)&'<BR>');
</CFSCRIPT>
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