I have a loop that saves to mongodb. and sometimes its a bit to fast and I get duplicate error.

I iterate over a object and send each to a check function.

import checkExists from './checkExists';

const obj = [
 {name: "Sven", age: 18},
 {name: "Svenie", age: 18},
 {name: "Svenjo", age: 18},
 {name: "Sven", age: 18},
 {name: "Svenja", age: 18},
};

for(let i = 0; i < obj.length: i++){
 checkExists(obj[i]);
}

in checkExists I check in mongodb schema if there is a document with the name.

import SaveNewUser from './SaveNewUser';

export default async function checkExists(data){
 const {name} = data;
 const amount = await User.find({"name": name}).select("name").lean();

 if(amount.lenght > 0){
    return;
 } else {
    return SaveNewUser(data);
 };
};

Then in SaveNewUser I save to database

export default function SaveNewUser(data){
 const {name, age} = data;
 const userData = {
    "name": secondary,
    "age": age,
 };

 const saveNewUser = new User(userData);
 saveNewUser.save().then(()=>{
    return;
 }).catch((err)=>{
    console.log(err);
 });
};

so, in the start loop there is a double, and it gets send fast to the checkIfExists function. both do not exists yet and get send to the SaveNewUser, where the first will save and the second returns the double error.

this is just an simple example of my code, and there might be more double and I need to check and save data as fast as possible. Does anyone know a good way to make sure I don't get the error? I could add the checkIfExists function to the save function, but its the same problem.

I am thinking of making a file to save temp data and filter that, but it seems like a ugly solution. I need all functions to be separated in different js files for modular use.

-- Update --

The loop can be executed multiple times from another script with new user object.