CognitoIdentityServiceProvider.signUP() doesn't accept user pool id? - node.js

Question

In the aws-sdk cognito documentation there is a function listed called signUp() that quote "Registers the user in the specified user pool and creates a user name, password, and user attributes." However, there is no parameter for a user pool Id. How exactly does one specify the user pool they want to add to? At first glance it thought maybe it was just missing in the documentation, but I tried adding UserPoolId as a property in the parameters object, to which it responded with an error about an unexpected field. There is also no function parameter to accept the pool id. My only other guess was that maybe the CognitoIdentityServiceProvider object accepted it in its constructor, but that also does not appear to be the case. I am aware that the API also provides the function AdminCreateUser() to add users, but don't want to use it if there's a better way.
documentation here https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/CognitoIdentityServiceProvider.html#signUp-property
Any ideas?

Answer 1

In Amazon Cognito, the User Pool ID is considered to be a sensitive piece of information, and it is used only in Admin API calls. The SignUp API call is not AWS SigV4 Signed, and it is meant to run on the browser side instead of the server side.
From the App Client ID, Cognito implicitly understands which User Pool you are referring to in your code. Hence, you can use the code in the documentation, and users will get added to your User Pool without the User Pool ID being a parameter in the API call.

Answer 2

Specify the App Client Id from the User Pool - not the User Pool Id. Create an App Client on the User Pool if you don't have one yet.
https://docs.aws.amazon.com/cognito/latest/developerguide/user-pool-settings-client-apps.html
The App Client Id is not considered secret from the AWS Cognito docs (but of course App Client Secret is - never include that anywhere on the client side). I've scratched out my App Client Id just to not broadcast here.
import {
CognitoIdentityServiceProvider
} from 'aws-sdk'
// make sure to use the same region as your user pool
const cognitoIdentityServiceProvider =
new CognitoIdentityServiceProvider({region: 'us-west-2'})
try {
const signUpResp =
await cognitoIdentityServiceProvider.signUp({
// Not UserPool ID but the ID for the "App Client" you have created on the User Pool
ClientId: '5orf...i67r',
Password: pw,
Username: email // i'm using email address for Username
}
).promise()
console.log(signUpResp)
} catch(e) {
alert(e.message || JSON.stringify(e));
}