How to make conditions and return a exception while resolving an array of promises-CodePudding

I have the next method

async findOne(id: string) {
  const coffee = await this.coffeeModel.findById(id);
  if (!coffee) throw new NotFoundException('coffee not found');
  return coffee;
}

But I want to check if in an array of coffees all exist so I am doing the following:

const coffeesPromises = []
arrayOfCoffees.forEach((element) => {
  coffeesPromises.push(this.findOne(element))
})

await Promise.all(coffeesPromises) 
//In case 1 coffee does not exist the API return
{
  "statusCode": 404,
  "message": "coffee not found",
  "error": "Not Found"
}

But when I try to wait for the coffee and make a condition with each coffee the error is thrown on the console (in case 1 coffee does not exist) and not as a JSON.

One way I tried to solved it was:

Promise.all(promises).then((results) =>
  results.forEach((result) => if (!result.sugar) throw new BadRequestException('coffee has no sugar'))
);

The way Im doing it is the next, but is slow, so that's why Im trying to improve it.

for (const coffee of arrayOfCoffees) {
  const coffeeDocuments = await this.findOne(coffee);
  if (!coffeeDocuments.sugar)
    throw new BadRequestException(
      `coffee has no sugar`,
    );
}

Which is the best way to handle this?

CodePudding user response：

Array.forEach technically ignores Promise(async/await). If you want to use Promise.all with array you'd better to use Array.map. The code would be something like this.

async findOne(id: string) {
  const coffee = await this.coffeeModel.findById(id);
  if (!coffee) throw new NotFoundException(`coffee ${id} not found`);
  return coffee;
}

const promises = arrayOfCoffees.map(async element => await this.findOne(element))

await Promise.all(promises).catch(e => /* error handling goes here */)

// or shortly
await Promise.all(arrayOfCoffees.map(async element => await this.findOne(element)))
             .catch(e => /* error handling goes here */)

As you can see the last line, I put an error handler to Promise.all. Because if Promise.all meets an error while running all the other promises it emits an error.

CodePudding user response：

change forEach with for (const item of items)