Axios random number of requests

问题:

I need to make multiple requests with Axios but I dont know how many, the number of requests is totally random and it could be 0 or 1 or 9182379, and after they are all done I need to do something, as if now I have to update my state(array of objects).

Do you have any idea how could I do this ??

let oldTickets = [...this.state.playedTickets];
let length = oldTickets.length;
let newTickets = [];

for (let index = 0; index < length; index++) {
  let currentTicket = oldTickets[index];

  // just imported function that returns axios.get call
  checkTickets(currentTicket.ticketNumber)
    .then(data => {

      let newTicket = {
        bla: bla
      }

      newTickets.push(newTicket);
      this.setState({playedTickets: newTickets})

    })
    .catch(err => {
      console.log(err);
    })

}

This is working fine but I know it's not good, so I am searching for better solution!

回答1:

after they are all done I need to do something

You can map the array to promises and use Promise.all:

Promise.all( // executes all requests in parallel
  this.state.playedTickets.map(({ ticketNumber }) => checkTickets(ticketNumber))
).then(playedTickets => { // or declare function as `async` and use `await`
  // executed only after all requests resolved
  console.log('tickets', playedTickets); 
  this.setState({ playedTickets });
}).catch(e => console.log(e)); // executed as soon as one request fails

EDIT:

continue awaiting for all requests even if some failed, and set the state based on the results of the successful requests

To achieve this, simply catch the error before passing to Promise.all:

Promise.all(
  this.state.playedTickets.map(({ ticketNumber }) =>
    checkTickets(ticketNumber).catch(console.log)
  )
).then(playedTickets => {
  console.log('tickets', playedTickets);
  this.setState({ playedTickets });
});

Failed requests will have undefined as the value in the array.
If required, you can filter them out with

const validTickets = playedTickets.filter(ticket => ticket !== undefined)