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So I posted this question Putting a simple expression language into java and got a great answer about using ScriptEngine to allow the user to write javascript which I did and it seemed to work

But whilst an expression like 

(artist.length>0 ? artist + '-' :'') + (album.length>0 ? album + '-' :'')

works using a full if statement does not 

if(artist.length>0) {artist + ':-'}   + (album.length>0 ? album + '-' :'')

You might ask why Im doing this, well I was hoping I could use an if:else if:else statement and this was a step towards that

share|improve this question
    
java != javascript ... –  Neal Jul 18 '11 at 18:14
    
@Neal: The OP is asking about JS code that's being run from Java, using JSR-223. Sometimes this kind of context matters, hence why the OP mentioned it. –  Chris Jester-Young Jul 18 '11 at 18:15

1 Answer 1

up vote 3 down vote accepted

That simply isn't valid javascript. The 

<cond> ? <iftrue> : <iffalse>

is the 'expression' form of if-else, and returns the value which can be used.

if {

} else {

}

is the 'statement' version, and is used to execute code, and does NOT return a value.

share|improve this answer
    
thanks you've exposed my javascript ignorance here, so is it possible for me to do the equivalent of if else if else in the expression –  Paul Taylor Jul 18 '11 at 18:27
    
You could nest the expressions, like a ? b : (c ? d : e), which translates to: If a, then b, else if c, then d, else e –  shelman Jul 18 '11 at 18:32
    
thanks that worked i.e (albumartist.length>0 ? albumartist :(artist.length>0 ? artist : ' ')) –  Paul Taylor Jul 18 '11 at 18:44

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