I am playing with the JDK Javascript API (JSR 223) and I wanted to check out the replacement of variables in a String. Then I suddenly got this error:

javax.script.ScriptException: sun.org.mozilla.javascript.internal.EvaluatorException: missing ; before statement (<Unknown source>#1) in <Unknown source> at line number 1

After some reseach I found out, that my variables did contain invalid characters in my case the variable contained a –.

So the Regular Expression for valid Javascript variable names is:

[a-zA-Z_$][0-9a-zA-Z_$]*

It is also possible to use any unicode characters for variables, but of course this is not recommended.