编写嵌套的Promise JavaScript ES6

Question

does anyone have any guides or tips on how to write a nested promises?

I am trying to turn the following nested for loop into a promise:

let arr = [1, 2, 3, 4, 5]


for (i = 0; i < arr.length ; i++) {

  for (j = i + 1; j < arr.length ; j++) {

      // call another asynchronous function

  }

}

I thought about doing Promise.all , but the iterator in the inside for loop starts at j = i + 1 so I wasn't sure how to handle this with Promise.all .

Thanks in advance!

Answer 1

Push them into an array

 let arr = [1, 2, 3, 4, 5] const promises = [] for (let i = 0; i < arr.length; i++) { for (let j = i + 1; j < arr.length; j++) { promises.push(new Promise((resolve, reject) => { setTimeout(resolve, 100, [i,j]); })); } } Promise.all(promises).then(values => { console.log(values); });