Sending extra params from angular application to keycloak

I am using angular as a front-end application and want to send some extra parameters to use. I am unable to find any relevant documentation for this. I have tried sending something in acr key but doesn’t work well. Here is the sample code I am using.

// initialization of keycloak instance
        config: {
            url: domain,
            realm: realm,
            clientId: client,
        initOptions: {
// At the time of login
// How could I pass extra Params over here?? e.g. tempId: 'abc'
this._keycloakInstance.login({redirectUri: 'http://localhost:4200/callback',scope :  'openid'}

and in which particular key I could get that. I am using script mapper in the keycloak.
Directly from postman I could add a param in x-www-form-urlencoded and can access this variable while getting token.