Detect-and-run a method in a Script Host using Java and FESI

[Jay]

Hi, Everybody:

I have a script host that implemented in Java and using FESI to run
JavaScript. The JavaScript files are separated into different files and
putting together at run or load time. Every time I have to manually to
make sure that a function referenced in one file is defined in another
so my host won't crash due to exception. I have been trying to put in a
detect-and-execute logic in my code for some time but with no real
success. This mainly due to FESI limitation. I believe only JavaScript
1.1 is supported. I have tried eval with try-catch but FESI won't allow
the key word "try" and "catch". I wonder if anybody in this group have
come across the similar problem? Any pointer would be very appreciated.

Thanks,

-Jay

 

[Martin Honnen]

I have tried eval with try-catch but FESI won't allow
the key word "try" and "catch".

Using
if (typeof someName != 'undefined')
or
if (typeof someName == 'function')
should work even if try/catch is not supported.

And you might consider to switch to the Mozilla Rhino engine instead of
FESI, it is a Java implementation as well but up to date to implement
JavaScript 1.5/ECMAScript edition 3 including try/catch.

 

[Jay]

Martin,

Thanks a lot for the pointers. Will let you know my findings.

Thanks again,

-Jay

 

[Jay]

Martin,

The typeof worked.
As side note to your response, your suggested code won't escape the
compilier check if it's run under JScript.Net and use MicroSoft VSA
engine as host. I happen to have two engines run side-by-side and one
is worked the other giving compilier error.

The Mozilla Rhino you mentioned sure gives me an option to substitute
the FESI.

Thanks again for your response,

-Jay