Microsoft ad b2c issue: policy is missing - node.js

Question

I made a chat bot which I want to authorize user using Azure ad b2c using OIDCStrategy. In the console, it always logs authentication failed due to: In collectInfoFromReq: policy is missing. The policy has been set in Azure. And I can't find somewhere to declare the policy in the code. Here is my server:
server.get('/login',
passport.authenticate('azuread-openidconnect',
{
failureRedirect:'/fail'
}),
function(req,res,next){
console.log('Login was called');
res.redirect('/',next);
}
)
server.post('/api/auth', passport.authenticate('azuread-openidconnect'));
And connection to the azure ad b2c:
passport.use(new OIDCStrategy({
redirectUrl:'http://localhost:3978/api/auth',
allowHttpForRedirectUrl:true,
clientID:'5fe844d7-e4d1-4c4c-ba70-078297b00abc',
clientSecret:'?aTvTEbwcNfUF2,^',
identityMetadata: 'https://login.microsoftonline.com/nuffieldbot.onmicrosoft.com/v2.0/.well-known/openid-configuration',
skipUserProfile: true,
responseType: 'code',
responseMode: 'form_post',
isB2C:true,
scope:['email','profile','offline_access','https://outlook.office.com/mail/read'],
loggingLevel:'info',
tenantName:'nuffieldbot.onmicrosoft.com',
passReqToCallback:true
},function(req, iss, sub, profile, accessToken, refreshToken, done){
log.info('Example:Email address we received was:', profile.email);
process.nextTick(function(){
findByEmail(profile.email,function(err,user){
if (err) {
return done(err);
}
if (!user){
users.push(profile);
return done(null, profile);
}
return done(null, user);
})
})
}
));
Where can I declare this policy in my code?

Answer 1

For B2C, we must have policy , if you have not set policy name in query string of request , it will throw error : In collectInfoFromReq: policy is missing . Please refer to source code of oidcstrategy.js :
// for B2C, we must have policy
if (self._options.isB2C && !params.policy)
return next(new Error('In collectInfoFromReq: policy is missing'));
You must set policy in request :
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You could also refer to code sample : Azure Active Directory OIDC Web Sample