Get from this link, there is a executable "jsc" in /System/Library/Frameworks/JavaScriptCore.framework/Versions/Current/Resources/. However, which is not in your path by default, so you need to create a link in your /bin:
sudo ln /System/Library/Frameworks/JavaScriptCore.framework/Versions/Current/Resources/jsc /bin/jsc
Then you can just type "jsc" in any command line to execute javascript statements. You can use "quit();" to exit.
ddh$ jsc
> [] + []
> [] + {}
[object Object]
> {} + []
0
> {} + {}
NaN
> quit();
ddh$
