Multiple asynchronous call in cascade in recursive function JS

Question

I already know this question has been asked many times but I can't figure out how to oganize my code. I'm coming from C/C++ language and still have the way of think, and what I'm writting in JS looks 'meaningless'.

I'm using a recursive function in order to generate a travel on a map. The thing is I need to make 2 asynchronous call of 2 different APIs, the second depending on the result of the first one.

Actually, i'm always using callback functions, like this :

    function asyncFunction(param, callbackF) {
      // ... //
      $.get(url, function(data, status) {
        callbackF(data, status);
      })
    }

    function asyncFunction2(param, callbackF) {
        // ... //
        $.get(url2, function(data, status) {
          callbackF(data, status);
        })
    }

    function recursiveFunction(param1, param2, num, tab, distance) {
      //.. stuff with parameters //
      asynFunction(param1, function(result, status) {
        // .. stuff with parameters .. //

        //.. Algo stops when distance is 0 ..//
        if(!distance) {
          asyncFunction2(param, function(data, status) {
            // Final stuff //

            return; // End
          });
        }
        else recursiveFunction(param1, param2, num, tab, distance); // parameters has been updated
      });
    }

recursiveFunction(param1, param2, num, tab, distance);

It's working but ugly with a lot of imbrication, and I can't event know if this function went wrong (ex. a call to an API failed, etc).

The question is how can I introduce Promises in this context or async/await terms in JS ? How can I turn this code into a more understanding way ?

Thanks.

Yury Tarabanko · Accepted Answer · 2020-04-24 11:25:12Z

1

$.get already returns a Promise-like object. You just need to get rid of callbacks and return the promise.

function asyncFunction(param) {
  // ... //
  return $.get(url)
}

function asyncFunction2(param) {
    // ... //
    return $.get(url2)
}

Now you can use async/await with your functions. Something like this should work

async function recursiveFunction(param1, param2, num, tab, distance) {
  const result = await asyncFunction(param1);
  // .. stuff with parameters .. //

  if(distance) {
    await recursiveFunction(param1, param2, num, tab, distance); // parameters has been updated
  } else {
    await asyncFunction2(param)
  }
}


recursiveFunction(param1, param2, num, tab, distance);

answered Apr 24, 2020 at 11:25

Yury Tarabanko

45.1k10 gold badges88 silver badges99 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

TheoB Over a year ago

Thanks, it's works like a charm and I get to know deeper about promises and asyn/await.

Collectives™ on Stack Overflow

Multiple asynchronous call in cascade in recursive function JS

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related