javascript - Fetch API until there is no data-CodePudding

I am using a restful API, and I need to post some data. but before, I need to ensure that the table is empty. The problem I am facing is that the delete method of this API return success, but does not immediately delete the data, this data is sent to a queue to delete asap.

So before I call the post method, I need to check if I have any items on this table. How can I call this method several times to ensure that the post method will only be executed when the table is empty?

async function run() {

    apiDelete()
    .then(() => console.log('deleting')) 
    .then(() => {

        getItems().
        then(() => {
            
            apiPost()
             .then(() => console.log('posting...'))
             .catch(e => console.log(e))
        })
       
      })
      .catch(e => console.log(e))     
     
  return

}

The methods:

async function apiPost() {
  const url = 'https://apipost.com/data/v2/1234'
  const options = {
    method: 'POST'
  }  
  return (await fetch(url, options)).json()
}

async function apiDelete() {
  const url = 'https://apidelete.com/data/v2/all'
  const options = {
    method: 'DELETE',    
  }
  return (await fetch(url, options)).json()
}

async function getItems() {
  const url = 'https://apiget.com/data/v2/all'
  const options = {
    method: 'GET',    
  }  
  return (await fetch(url, options)).json()
}

CodePudding user response：

You need to make a recursive call with an exit condition that asks it to exit when the number of elements is 0.

One way could be something like this:

async function deleteUntilEmpty() {
  await apiDelete();
  const items = await getItems();

  if (items.length) {
    return deleteUntilEmpty();
  }
}

async function run() {
  await deleteUntilEmpty();
  apiPost()
    .then(() => console.log("posting..."))
    .catch((e) => console.log(e));
}

Instead of deleting constantly, you might as well just poll to see if the server has completed the original delete:

async function checkIsEmpty() {
  const items = await getItems();

  if (items.length) {
    return checkIsEmpty();
  }
}

async function deleteAndPollUntilEmpty() {
  await apiDelete();
  await checkIsEmpty();
}

async function run() {
  await deleteAndPollUntilEmpty();
  apiPost()
    .then(() => console.log("posting..."))
    .catch((e) => console.log(e));
}