User Guide

132 Chapter 6: Extending ColdFusion Pages with CFML Scripting
Note: The test expression is re-evaluated before each repeat of the loop. If code inside the loop
changes any part of the test expression, it can affect the number of iterations in the loop.
The statement can be a single semicolon terminated statement or a statement block in curly
braces.
When ColdFusion executes a for loop, it does the following:
1. Evaluates the initial expression.
2. Evaluates the test-expression.
3. If the test-expression is False, exits the loop and processing continues following the statement.
If the test-expression is True:
a Executes the statement (or statement block).
b Evaluates the final-expression.
c Returns to Step 2.
For loops are most commonly used for processing in which an index variable is incremented each
time through the loop, but it is not limited to this use.
The following simple for loop sets each element in a 10-element array with its index number.
for(index=1;
index LT 10;
index = index + 1)
a[index]=index;
The following, more complex, example demonstrates two features:
• The use of curly braces to group multiple statements into a single block.
• An empty condition statement. All loop control logic is in the statement block.
<cfscript>
strings=ArrayNew(1);
ArraySet(strings, 1, 10, "lock");
strings[5]="key";
indx=0;
for( ; ; ) {
indx=indx+1;
if(Find("key",strings[indx],1)) {
WriteOutput("Found key at " & indx & ".<br>");
break;
}
else if (indx IS ArrayLen(strings)) {
WriteOutput("Exited at " & indx & ".<br>");
break;
}
}
</cfscript>
This example shows one important issue that you must remember when creating loops: you must
always ensure that the loop ends. If this example lacked the
else if statement, and there was no
“key” in the array, ColdFusion would loop forever or until a system error occurred; you would
have to stop the server to end the loop.