public static Function getFunction(Scriptable obj, String functionName) {
Object x = ScriptableObject.getProperty(obj, functionName);
if (x == Scriptable.NOT_FOUND) {
// This method used to swallow the exception from calling
// an undefined method. People have come to depend on this
// somewhat dubious behavior. It allows people to avoid
// implementing listener methods that they don't care about,
// for instance.
return null;
}
if (!(x instanceof Function)) throw ScriptRuntime.notFunctionError(x, functionName);
return (Function) x;
}
