如何将异步函数推送到数组而不执行未来的 Promise.all

Question

I have some async functions that make calls to a REST API and return the result. I want to use Promise.all to call several of these functions at once and await the full result. I understand how Promise.all works and this isn't a problem with Promise.all. This is a problem with using Array.push to dynamically create an array of the async functions I want to call.

So here's the scenario. A user of my app loads a page. That page needs to retrieve data from an API. It uses those async functions I mentioned to do that. However, the data the page needs to retrieve is different depending on the parameters set. So sometimes, it may need to retrieve a list of users, a specific customer, and a specific project. Other times, it may need to get all users and all projects and no customers.

So my code looks something like this:

created() {
  let promiseList = []
  if (options.getCustomers) { promiseList.push(listCustomers())
  if (options.getCustomer) { promiseList.push(getCustomer(customerId)) }
  if (options.getUsers) { promiseList.push(getUsers()) }
  await Promise.all(promiseList)
}

So this works to some degree. Promise.all is working just fine. The problem is that I can't push a function to an array without it being called immediately. Therefore, each of the functions that I'm pushing to the promiseList array gets called twice: immediately and again with Promise.all.

How can I push the async function to the array as a reference so that it's not executed immediately?

Answer 1

Put in the array the reference to the function and call then with a map when you use the Promise.all

created() {
  let promiseList = []
  if (options.getCustomers) { promiseList.push({ func: listCustomers })
  if (options.getCustomer) { promiseList.push({ func: getCustomer, arg: customerId}) }
  if (options.getUsers) { promiseList.push({ func: getUsers }) }
  await Promise.all(promiseList.map( (prom) => prom.func(prom.arg) ))
}

Answer 2

You can also push the function

created() {
     let promiseTasks = []; // meaning name is better
     if (options.getCustomers) {
         promiseTasks.push(() => listCustomers());
     }
     if (options.getCustomer) {
         promiseTasks.push(() => getCustomer(customerId));
     }
     if (options.getUsers) {
         promiseTasks.push(() => getUsers());
     }

     await Promise.all(promiseTasks.map((func) => func()));
 }

Note: I don't think it's the use case you want to use Promise.all, because its looks like all get requests, and it's better to be separated to different endpoints.

Request option is useally can be options like: limit, sort, projection, populateQuery, preventPopulate.