Mollitia

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Fallback ​

The Fallback module allows you to filter your errors.

Usage ​

Works very well in conjunction with other modules! For example, filtering Circuit Breaker errors to return a generic error.

typescript
import * as Mollitia from 'mollitia';
// Creates a circuit
const circuit = new Mollitia.Circuit({
  options: {
    modules: [
      // Creates a fallback module
      new Mollitia.Fallback({
        callback (err) {
          // Every time the method rejects, You can filter here
          if (err instanceof MyError) {
            // I know this error
            return err; 
          }
          return new UnknownError();
        }
      })
    ]
  }
});

// The rejected errors are filtered, meaning you always know what is returned here
circuit.fn(myFunction).execute()
  .catch((err) => {
    if (err instanceof MyError) {
      // It's a MyError error
    } else {
      // It's an UnknownError error
    }
  });
import * as Mollitia from 'mollitia';
// Creates a circuit
const circuit = new Mollitia.Circuit({
  options: {
    modules: [
      // Creates a fallback module
      new Mollitia.Fallback({
        callback (err) {
          // Every time the method rejects, You can filter here
          if (err instanceof MyError) {
            // I know this error
            return err; 
          }
          return new UnknownError();
        }
      })
    ]
  }
});

// The rejected errors are filtered, meaning you always know what is returned here
circuit.fn(myFunction).execute()
  .catch((err) => {
    if (err instanceof MyError) {
      // It's a MyError error
    } else {
      // It's an UnknownError error
    }
  });

API Reference ​

Options ​

NameDescriptionDefault
callbackThe callback, called when the circuit rejects.Function(Error)

Methods ​

NameDescriptionReturns
getExecParams()Returns the circuit function parameters.any[] params

Events ​

NameDescriptionParams
executeCalled when the module is executed.Mollitia.Circuit circuit, Promise<T> promise, any[] params