Can ScriptEngineManager give me the name of the Javascript function it has just compiled in Java

Question

How do I find out the name of a javascript function parsed in Java. I allow a user to type in a Javascript function (in a JTextArea), then I use ScriptEngineManager to confirm it is valid syntax as follows:

public final boolean isFunctionValid(String function)
{
    try
    {
        ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = manager.getEngineByName("JavaScript");
        Object result = engine.eval(function);
    }
    catch(ScriptException se)
    {
        return false;
    }
    return true;
}

Works fine, but I also want to know the name of the function so I can assign the function a name that matches the function name. Id prefer it if ScriptEngineManager does it for me rather tham me trying to work it out by parsing the variable function with al the inherent risks of that approach

EDIT As it seems there is no way to properly do this, Ive created two checks using regular expressions that work for me.

    protected static Pattern functionNameMatch;
    protected static Pattern multipleFunctionsMatch;
    static
    {
        functionNameMatch = Pattern.compile("function[ ]+([a-zA-Z0-9]*)[ ]*\\(");
        multipleFunctionsMatch = Pattern.compile("function[ ]+");
    }


    protected boolean isOneFunction()
    {
        Matcher m = multipleFunctionsMatch.matcher(function.getText());
        if(m.find())
        {
            if(m.find())
            {
                return false;
            }
            return true;
        }
        return false;
    }

    protected String deriveNameFromFunction()
    {
        Matcher m = functionNameMatch.matcher(function.getText());
        if(m.find())
        {
            return m.group(1);
        }
        return "";
    }

Well you really have no way of knowing whether the text that was parsed was even a function at all. Any valid JavaScript statements would succeed that test. I'm pretty sure the answer is "no". — Pointy, Aug 30 '12 at 20:23
Hmm, yes did occur to be after posting that it is just checking it is valid Javascript syntax rather a Javscript Function, but surely there must be a robust way to do both (check its a javascripit function, and its name) — Paul Taylor, Aug 30 '12 at 20:47
JavaScript is sufficiently flexible that there's really no way to do that, short of instrumenting Rhino to provide that sort of statistic. JavaScript functions don't even have to *have* names. — Pointy, Aug 30 '12 at 20:53
Okay. not the answer I orignally hoped for, but thanks no big deal. — Paul Taylor, Aug 31 '12 at 08:24

score 0 · Accepted Answer · edited Nov 26 '13 at 18:10

So as it was not possible in JavaScript, I do some additional checks using pattern matching instead

protected static Pattern functionNameMatch;
protected static Pattern multipleFunctionsMatch;
static
{
    //TODO this method only works if all parameters are put on first line of function, otherwise declares function
    //is invalid
    functionNameMatch = Pattern.compile("function[ ]+([a-zA-Z0-9]*[ ]*\\(.*\\))");
    multipleFunctionsMatch = Pattern.compile("function[ ]+");
}

protected boolean isOneFunction()
{
    Matcher m = multipleFunctionsMatch.matcher(function.getText());
    if(m.find())
    {
        if(m.find())
        {
            return false;
        }
        return true;
    }
    return false;
}

protected String deriveNameFromFunction()
{
    Matcher m = functionNameMatch.matcher(function.getText());
    if(m.find())
    {
        return m.group(1);
    }
    return "";
}

Can ScriptEngineManager give me the name of the Javascript function it has just compiled in Java

1 Answers1