Axios: chaining multiple API requests

A little late to the party, but I like this pattern of chaining promises, returning them to keep the promise chain alive.

axios
  .get('https://maps.googleapis.com/maps/api/geocode/json?&address=' + this.props.p1)
  .then(response => {
    this.setState({ p1Location: response.data });
    return axios.get('https://maps.googleapis.com/maps/api/geocode/json?&address=' + this.props.p2);
  })
  .then(response => {
    this.setState({ p2Location: response.data });
    return axios.get('https://maps.googleapis.com/maps/api/geocode/json?&address=' + this.props.p3);
  })
  .then(response => {
    this.setState({ p3Location: response.data });
  }).catch(error => console.log(error.response));

For better performance and cleaner code:

1. Use promise.all() or axios.all() to execute request1 and request2 at the same time. So request2 will execute without waiting for request1 response. After request1 and request2 return the response, request3 will continue execute based on the returned response data as parameter.
2. Template Strings use back-ticks (``)

async componentDidMount(){
    try{
        const [request1, request2] = await Promise.all([
           axios.get(`https://maps.googleapis.com/maps/api/geocode/json?&address=${this.props.p1}`),
           axios.get(`https://maps.googleapis.com/maps/api/geocode/json?&address=${this.props.p2}`)
        ]);

        const request3 = await axios.get(`https://maps.googleapis.com/maps/api/directions/json?origin=place_id:${request1.data.results.place_id}&destination=place_id:${request2.data.results.place_id}&key=${API-KEY-HIDDEN}`);
        console.log(request3);
    }
    catch(err){
        console.log(err)
    }
}

For simultaneous requests with axios, you can use axios.all() plus axios.spread()

axios.spread() is used to spread the array of arguments into multiple arguments, so that all data can be passed to the function.

Example

const url_1 = '', url_2 = ''; 

axios.all([
  axios.get(url_1), 
  axios.get(url_2)
])
  .then(
     axios.spread((resp1, resp2) => {
       let id_1 = resp1.data.results.place_id
       let id_2 = resp2.data.results.place_id
       let url_3 = ''                          // <---- Build your third URL here
       axios.get(url_3)
         .then((resp3) => {
             // You have all the data available here to useState()
         })
     })
  )
  .catch((error) => console.log(error)) 

create array of promise and then use reduce.

/**
 * Runs promises from array of functions that can return promises
 * in chained manner
 *
 * @param {array} arr - promise arr
 * @return {Object} promise object
 */
function runPromiseInSequence(arr, input) {
  return arr.reduce(
    (promiseChain, currentFunction) => promiseChain.then(currentFunction),
    Promise.resolve(input)
  )
}

// promise function 1
function p1(a) {
  return new Promise((resolve, reject) => {
    resolve(a * 5)
  })
}

// promise function 2
function p2(a) {
  return new Promise((resolve, reject) => {
    resolve(a * 2)
  })
}

// function 3  - will be wrapped in a resolved promise by .then()
function f3(a) {
 return a * 3
}

// promise function 4
function p4(a) {
  return new Promise((resolve, reject) => {
    resolve(a * 4)
  })
}

const promiseArr = [p1, p2, f3, p4]
runPromiseInSequence(promiseArr, 10)
  .then(console.log)   // 1200