I have a node application with passport library. I use passport strategy like this:

passport.use(someStrategy)

Is it possible to override that strategy later on dynamically? During the application run, I would want to at some point use a different strategy. Actually same strategy, but with a different configuration.

If I just make another passport.use(someOtherStrategy), then doesn't that just add another 'middleware' to passport? Then that wouldn't delete the old one, just add one more. I would want the old one to be deleted. So either override, or delete and add a new one.

I have a node application with passport library. I use passport strategy like this:

passport.use(someStrategy)

Is it possible to override that strategy later on dynamically? During the application run, I would want to at some point use a different strategy. Actually same strategy, but with a different configuration.

If I just make another passport.use(someOtherStrategy), then doesn't that just add another 'middleware' to passport? Then that wouldn't delete the old one, just add one more. I would want the old one to be deleted. So either override, or delete and add a new one.

• javascript
• node.js
• passport.js

2 Answers 2

Digging in passport source code revealed that overriding can be done easily. Here is the relevant part of the code:

Authenticator.prototype.use = function(name, strategy) {
  if (!strategy) {
    strategy = name;
    name = strategy.name;
  }
  if (!name) { throw new Error('Authentication strategies must have a name'); }

  this._strategies[name] = strategy;
  return this;
};
...
...
Authenticator.prototype.unuse = function(name) {
  delete this._strategies[name];
  return this;
};

As can be seen from the code, if the strategy that you use has a name that is already used by another strategy in the _strategies list, then it is replaced by the new strategy. Also one can delete the strategy with method unuse, as seen in the code also.

@Mitch Your answer is helpfull, but little off-topic. Probably partly because I was not super clear that I was searching for a way to override an existing strategy, not just how to configure multiple strategies. Sorry, I wasn't super clear in my question description.

It's possible to configure multiple named strategies in passport, even of the same type. Below I can have two instances of myStrategy with different configs, but named differently,

For example:

passport.use('someStrategy', new myStrategy(options))
passport.use('anotherStrategy', new myStrategy(differentOptions));

Then later, when authenticating you can specify which strategy to use:

passport.authenticate('someStrategy', ...);

Using the above, you can configure multiple strategies, and based on a conditional, decide which strategy to use:

if (condition){
    passport.authenticate('someStrategy', ...);
}
else{
    passport.authenticate('anotherStrategy', ...);
}

Or:

let strategyToUse = determineStrategy(); //dynamically choose which strategy you want
passport.authenticate(strategyToUse, ...);

Deleting the strategy from the middleware stack is a little trickier and there's no inbuilt function to do it I don't think. It may involve splicing the strategy out of the stack manually. This question might help you with removing middleware from the stack; its aimed towards express/connect so should also apply to passport to some extent.