google script how to call library functions dynamically?

google script how to call library functions dynamically?

I have a set of libraries that have the same functions in each (each
library is associated with a template and every time different templates
can be used, depending on the user request). I am trying to create a code
that will call functions dynamically. This is fine as long as the
functions are in the same script. However, my functions are in different
libraries and when I try to call them I get an error: Execution failed:
TypeError: Cannot find function Script2.getItBack in object [object
Object]. (line 25, file "dynamicFunctionsTest").
Here is the code:
function test1() {
return 'raining';
}
function test2() {
return 'cats';
}
function test3() {
return ScriptLibrary1.returnWord(); // the function returns the word
'and'
}
function testing() {
var message;
var func = [];
func [0] = 'test1';
func [1] = 'test2';
func [2] = 'test3';
func [3] = 'ScriptLibrary2.returnWord'; // the function returns the
word 'dogs'
Browser.msgBox(func); // check values before calling
for (var i = 0; i < func.length ; ++i) {
message = this[func[i]](); // this line fails on the 4th
one
Browser.msgBox(message);
}
}
I am getting the first 3 working (the third was just a test to see if I
can call locally which works but is insufficient for my purpose), but it
fails on the 4th one.
Anyone has any idea how to get it to work?
Thanks.