Combine multiple observable arrays into new object array

Question

I have 3 observable arrays like below.

persons = [
   {
      \"firstName\":\"john\",
      \"lastName\":\"public\",
      \"locationID\":\"1\",
      \"depa         


        

Answer 1

It's not clear what exactly your observables are emitting, so I considered two options.

let persons = [
    {
        "firstName":"john",
        "lastName":"public",
        "locationID":"1",
        "departmentID":"100"
    },
    {
        "firstName":"sam",
        "lastName":"smith",
        "locationID":"2",
        "departmentID":"101"
    }
];

let departments = [
    {"departmentID": "100", "name": "development"},
    {"departmentID": "101", "name": "sales"}
];

let locations = [
    {"locationID": "1", "name": "chicago"},
    {"locationID": "2", "name": "ny"}
];

// Option 1: first observable emits persons one by one, 
// locations and departments are emitted as whole arrays.
let o1: any = Observable.from(persons);
let o2: any = Observable.of(departments);
let o3: any = Observable.of(locations);

o1.withLatestFrom(o2, o3, (p, d, l) => {
    // here it is probably better to convert array to some kind of map or dictionary,
    // but I'm only showing Rxjs concept of doing such things.
    let location = l.find(c => c.locationID === p.locationID);
    let department = d.find(c => c.departmentID === p.departmentID);
    return {
        firstName: p.firstName,
        lastName: p.lastName,
        location: location ? location.name : "",
        department: department ? department.name : ""
    };
}).subscribe((f) => {
    console.log(f);
});

// Option 2: all observables emit elements one by one.
// In this case we need to convert departments and locations to arrays.
o1 = Observable.from(persons);
o2 = Observable.from(departments);
o3 = Observable.from(locations);

o1.withLatestFrom(o2.toArray(), o3.toArray(), (p, d, l) => {
    // this part of code is exactly the same as in previous case.
    let location = l.find(c => c.locationID === p.locationID);
    let department = d.find(c => c.departmentID === p.departmentID);
    return {
        firstName: p.firstName,
        lastName: p.lastName,
        location: location ? location.name : "",
        department: department ? department.name : ""
    };
}).subscribe((f) => {
    console.log(f);
});