String concatenation isn't working

[radmilabord]

I'm creating graph string like this:
var graph='a-->b\n'+
'b-->c\n';

then I assign string to the div. it works.
However if I try:
var graph='a-->b\n';
graph+='b-->c\n';

it does not work. I get text displayed on the screen and no graph.
I'd like to put in some variables and conditions into chart string, but does not seem like it is possible.

Thanks,
Radmila