How to check if a variable is not defined, inside an expression, without getting Error: Undefined symbol

[tedeschia]

Is it possible to check for undefined variables inside an expression, before the expression evaluation throws the error "Undefined symbol"?

I'm using the lib to run expressions written by the user, and injecting some external variables as scope.

But I would need to let the user check if some variable exists in the expression logic, and proceed accordingly.

ie:
someVar==undefined?someDefaultResult:someVar+1.

If I try this kind of expression, it doesn't get evaluated, throwing the "Undefined symbol" error instead

[josdejong]

See: #2865, #1414, #660

Maybe onUndefinedSymbol is all you need.

[tedeschia]

yes, it was a very simple solution:
mathInstance.SymbolNode.onUndefinedSymbol = () => null;
thanks!