Reduce a list of users and a list of roles for each user into a single unified listing of users.

javascript.js

const data = JSON.parse(`{
    "users": [
        {
            "id": 1,
            "name": "basicuser"
        },
        {
            "id": 2,
            "name": "adminuser"
        }
    ],
    "userroles": [
        {
            "id": 7,
            "user_id": 1,
            "role": "BASIC"
        },
        {
            "id": 8,
            "user_id": 2,
            "role": "ADMIN"
        }
    ]
}`)

let users = []

data.users.forEach(u => {
  users.push({roles: data.userroles.filter( r => 
    r.user_id === u.id 
  ).map(
    r => r.role
  ), ...u})
})

console.log(users)

python3.py

import json

data = json.loads("""{
    "users": [
        {
            "id": 1,
            "name": "basicuser"
        },
        {
            "id": 2,
            "name": "adminuser"
        }
    ],
    "userroles": [
        {
            "id": 7,
            "user_id": 1,
            "role": "BASIC"
        },
        {
            "id": 8,
            "user_id": 2,
            "role": "ADMIN"
        }
    ]
}""")

users = []

for u in data['users']:
    users.append(dict(roles=list(map(lambda r: r['role'], filter(lambda r: r['user_id'] == u['id'], data['userroles']))), **u))

print(users)