Step 4 | Cognito Identity Pool

1. Using the CLI, create new identity pool, named DynamoPool, allow unauthenticated identities to access our DynamoDB table. 
    aws cognito-identity create-identity-pool \
    --identity-pool-name DynamoPool \
    --allow-unauthenticated-identities \
    --output json
2. Create an IAM role named Cognito_DynamoPoolUnauth. This is the role that will be assumed by our Cognito identity pool, which will give it access to our DynamoDB. 
aws iam create-role --role-name Cognito_DynamoPoolUnauth --assume-role-policy-document file://myCognitoPolicy.json --output json

3. Grant the Cognito_DynamoPoolUnauth role read access to DynamoDB by attaching a managed policy (AmazonDynamoDBReadOnlyAccess).
aws iam attach-role-policy --policy-arn arn:aws:iam::aws:policy/AmazonDynamoDBReadOnlyAccess --role-name Cognito_DynamoPoolUnauth

4. To double check that our role has been set up correctly. 
aws iam get-role --role-name Cognito_DynamoPoolUnauth --output json

5. Add our role to the Cognito Identity Pool. Replace the pool ID with your own pool ID and use the role ARN from the previous step.

aws cognito-identity set-identity-pool-roles \
--identity-pool-id "us-east-1:0fa09c3e-03d6-4f01-9911-a103e9b5f76a" \
--roles unauthenticated=arn:aws:iam::721944718279:role/Cognito_DynamoPoolUnauth --output json

Double check it worked using: 
aws cognito-identity get-identity-pool-roles  --identity-pool-id "us-east-1:0fa09c3e-03d6-4f01-9911-a103e9b5f76a"

We can now specify the Cognito credentials in our application to be modified in the index.html
Add this snippet to our index.html:

AWS.config.credentials = new AWS.CognitoIdentityCredentials({
IdentityPoolId: "us-east-1:0fa09c3e-03d6-4f01-9911-a103e9b5f76a",
RoleArn: "arn:aws:iam::721944718279:role/Cognito_DynamoPoolUnauth"
});