Using Highland.js to hydrate one stream with data from another - node.js

Question

Say I have two Highland streams:
import hl from 'highland'
const accounts = hl([
{id: 1, name: "Bob"},
{id: 2, name: "Chris"},
]);
const accountData = hl([
{id: 1, age: 21},
{id: 2, age: 43},
]);
I'd like to map over the accounts stream and merge in the extra data from accountData so the result looks something like this:
Highland.Stream<[
{id: 1, name: "Bob", age: 21},
{id: 2, name: "Chris", age: 43},
]>
This is something that's pretty simple with normal arrays but I was wondering if it were possible when using streams.

Answer 1

import hl from 'highland';
const accounts = hl([
{ id: 1, name: 'Bob' },
{ id: 2, name: 'Chris' }
]);
const accountData = hl([
{ id: 1, age: 21 },
{ id: 2, age: 43 }
]);
hl([ accounts, accountData ])
.merge()
.reduce(new Map(), (accum, account) => {
const { id } = account;
const mergedAccount = Object.assign({}, accum.get(id), account);
return accum.set(id, mergedAccount);
})
.map(map => [ ...map.values() ])
.doto(console.log)
.done(() => {});
Output:
[
{ id: 1, name: 'Bob', age: 21 },
{ id: 2, name: 'Chris', age: 43 }
]