JS Filter array to remove duplicate values based on condition

Question

I have an array containing duplicate elemnets

let myArray=[
     {role: "role-1", deviceId: ""},
     {role: "role-2", deviceId: "d-2"},
     {role: "role-3", deviceId: "d-3"},
     {role: "role-1", deviceId: "d-1"},
     {role: "role-2", deviceId: ""},
     {role: "role-4", deviceId: ""}
     {role: "role-5", deviceId: ""}
]

I want to remove the duplicate roles and have array which contains roles without empty("") deviceIds and if deviceId is empty keep only one role without duplicates in this way

myArray=[
         {role: "role-1", deviceId: "d-1"},
         {role: "role-2", deviceId: "d-2"},
         {role: "role-3", deviceId: "d-3"}
         {role: "role-4", deviceId: ""}
         {role: "role-5", deviceId: ""}

 ]

I have written the function in this way

function dedupeByKey(arr, key) {
  const temp = arr.map(el => el[key]);
  return arr.filter((el, i) =>
    temp.indexOf(el[key]) === i
  );
}

console.log(dedupeByKey(myArray, 'role'));

But in the result, its not checking to give priority for deviceId with values and role with empty deviceId is getting added. How to fix this?

Answer 1

You can use reduce with default to object, and if you need, you can convert it to array at the end.

let myArray = [
     {role: "role-1", deviceId: ""},
     {role: "role-2", deviceId: "d-2"},
     {role: "role-3", deviceId: "d-3"},
     {role: "role-1", deviceId: "d-1"},
     {role: "role-2", deviceId: ""},
     {role: "role-4", deviceId: ""},
     {role: "role-5", deviceId: ""}
]

const res = myArray.reduce((agg, itr) => {
  if (agg[itr.role]) return agg // if deviceId already exist, skip this iteration
  agg[itr.role] = itr.deviceId  // if deviceId not exist, Add it
  return agg
}, {})

let make_array = Object.keys(res).map(key => { return { role: key, deviceId: res[key] }})

console.log(make_array)