How to wait until Javascript forEach loop is finished before proceeding to next sep

user_2664815 0
Viewed 6594

I need to wait for all of the axios calls in a function called by a forEach loop to run before I call another function to reload data that should be updated by the axios calls.

function1() {
    let arr = [1, 2, 3, 4, 5];
    arr.forEach((num) => {
        function2(num);
    });
    //Wait until each call in the forEach loop above
    //is done before running the function3() function.
    function3();
}

function2(number) {
    axios.post('/internal-url/action/' + number)
        .then((response) => {
            return response;
        });
}

function3() {
    console.log('reloading data...');
    /* DB call to reload data */
    console.log('data is reloaded');
}

The problem here is that the data reloads before the axios calls are complete. I know the axios calls worked because I can see they updated in the database, but I need for function1() to wait for all of the axios calls in function2() to finish before running the reload in function3().

I've tried to make function1() and function2() async/await functions, both at the same time and then individually, but that did not work. How would I go about doing this specifically?

axios async-await asynchronous foreach javascript
3 Answers

Create an array of promises then use Promise.all to await their resolution/rejection using async/await.

// async/await - create an array of promises
// from function2, then await until Promise.all has
// fully resolved/rejected
async function1() {
  let arr = [1, 2, 3, 4, 5];
  const promises = arr.map((num) => function2(num));
  await Promise.all(promises);
  function3();
}

function2(number) {
  return axios.post('/internal-url/action/' + number);
}

function3() {
  console.log('reloading data...');
  /* DB call to reload data */
  console.log('data is reloaded');
}
user_13770020

The best solution would be to use Promise.all so all the requests can be made in parallel. This would look something like this.

function1() {
    let arr = [1, 2, 3, 4, 5];
    Promise.all(arr.map((num) => function2(num))).then(() => {
        function3();
    });
}

This will wait until all of the promises that function2 returned have been resolved before calling function3.

user_14598380

Maybe like this:

const arr = [1, 2, 3, 4, 5];
let index = 0;
const answers = [];
(function loop() {
    const value = arr[index];
    function2(value).then(res => {
        answers.push(res);
    });
    index++;
    if (index < arr.length) {
        loop();
    }
})();
function3();
console.log(answers);
user_47214630
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