IBM Cloud Function for App ID sign_up and forgot_password

I can generate token from cloud with following cloud function

const main = (params) => {
    return new Promise(function (resolve, reject) {
        request({
            url: credentials.oauthServerUrl + '/token',
            method: 'POST',
            auth: {
                username: credentials.clientId,
                password: credentials.secret
            },
            form: {
                grant_type: "password",
                username: params.uid,
                password: params.pwd
            }
        }, function (error, response, body) {
            resolve(response);
        })
    })
}

How i can use App ID sign_up and forgot_password functionality without Node.js SDK and Express server. In other words i'd like to keep my app (SPA) serverless and use cloud functions. I have tried, and read docs for a solution, but no luck so far (http 404).

Edit: function that i tried to invoke forgot password page but result is error (statusCode 400) "missing redirect"

const main = (params) => {
    return new Promise(function (resolve, reject) {
        request({
            url: credentials.oauthServerUrl + '/forgot_password',
            method: 'GET',
            form: {
                client_id: credentials.clientId,
                redirect_uri: "http://www.google.fi"
            }
        }, function (error, response, body) {
            resolve(response);
        })
    })
}

And the working solution seemed to be following:

const request = require('request');
const credentials = {
  "version": 3,
  "clientId": "xxx",
  "secret": "xxx",
  "tenantId": "xxx",
  "oauthServerUrl": "https://appid-oauth.eu-gb.bluemix.net/oauth/v3/xxx/cloud_directory/forgot_password"
}
const main = (params) => {
    return new Promise(function (resolve, reject) {
        request({
            url: credentials.oauthServerUrl 
                + '?client_id=' + credentials.clientId 
                    + '&redirect_uri=http://www.my.domain'
                ,
            method: 'GET'
        }, function (error, response, body) {
            resolve(response);
        })
    })
}