Postman pre-request script to automatically get a bearer token from Auth0 and save it for reuse

postman-pre-request-to-get-token.js

const echoPostRequest = {
  url: pm.environment.get('api_url'),
  method: 'POST',
  header: 'Content-Type:application/json',
  body: {
    mode: 'application/json',
    raw: JSON.stringify(
        {
        	client_id:pm.environment.get('client_id'),
        	client_secret:pm.environment.get('client_secret'),
        	grant_type:pm.environment.get('grant_type'),
            grant_type:pm.environment.get('scope'),
            username:pm.environment.get('username_admin'),
            password:pm.environment.get('password_admin'),
        })
  }
};

var getToken = true;

if (!pm.environment.get('expires_in') || 
    !pm.environment.get('access_token')) {
    console.log('Token or expiry date are missing')
    getToken = true;
} else if (pm.environment.get('expires_in') <= (new Date()).getTime()) {
    console.log('Token is expired')
    getToken = true;
} else {
    getToken = false;
    console.log('Token and expiry date are all good');
}

if (getToken === true) {
    pm.sendRequest(echoPostRequest, function (err, res) {
    console.log(err ? err : res.json());
        if (err === null) {
            console.log('Saving the token and expiry date')
            var responseJson = res.json();
            pm.environment.set('access_token', responseJson.access_token)
    
            var expiryDate = new Date();
            expiryDate.setSeconds(expiryDate.getSeconds() + responseJson.expires_in);
            pm.environment.set('expires_in', expiryDate.getTime());
        }
    });
}