Testcomplete 12 TcxListBox Selection at Runtime from Code not working

This is one of the differences between JScript and JavaScript.  You cannot set the value of parameterized properties directly.  You need to use the $set method.  See

https://support.smartbear.com/testcomplete/docs/scripting/specifics/javascript-for-jscript-users.html

Quote:

JScript lets you assign values to parameterized properties directly:

JScript

 

obj.wValue(3, 5) = newValue;

 

JavaScript does not support this syntax. You need to use the $set method instead:

JavaScript

 

obj.$set("wValue", 3, 5, newValue);