asked on

Async/Await run a number of functions in it's given order

If I need to run an unknown number of functions in a specific order what is the best way to do this using Async await?

For example...if I have:

function func1() { //does something }
function anotherfunc() { //does something }
function func3() { //does something }

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The number of functions above could be 3 or 10.

Then using async away, I need to call them in order:

So I have another function called process:

function process() {
  func3(); 
 func1();
 anotherfunc() ;
}

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function process needs to run the functions in the order that they are placed and each has to finish before the other one starts.

How can I do this?

David Johnson, CD

you can't do them in order as each is dependant upon the previous results.

error2013

ASKER

All I want is:

run function1 and wait for it to finish...
run function2 and wait for it to finish...
run function3 and wait for it to finish...

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etc ...using Async / wait

Like promise.all

David Johnson, CD

then why use async /wait if they need to be run one after the other
you can use 1 async/await and do all 3 allowing UI to continue

David Favor

1) You can start any number of functions in a given order. That's up to you. However you start your functions, just setup whatever order you like.

2) You can only start functions in a given order. When running async, you'll have no control over when functions complete. That's the nature of async, so starting them in a particular order... seems... doesn't seem to be much use, other than for initial debugging maybe.

error2013

ASKER

So async / await without promises cannot run functions in an order like Promise.All does?

David Johnson, CD

Entirely different processes and rules of behaviour

David Favor

With async... async means 100% async...

You can arrange to start processes... however you start them, in any order.

They they run on their own as a herd. Each function will end, when it ends, with no ordering... unless you somehow inject yields into the functions via some mechanism.

ASKER CERTIFIED SOLUTION

Julian Hansen

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Julian Hansen

@David

then why use async /wait if they need to be run one after the other
you can use 1 async/await and do all 3 allowing UI to continue

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But that is what async / await does - it does not pause the UI it is just a short hand for

promise.then(resp => console.log('do something'));

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It will not stop the UI - all it does is ensures that the line after the await line runs after the await call is finished but normal execution continues.

Member_2_5296602

this might clear it up a bit I hope

function oneAsync() {
  const TIMEOUT_MS = 3000;
  
  return new Promise((resolve, reject) => { 
    setTimeout(() => {
      const result = 'one';
      console.log('doing function one => ', result);

      if (result) {
        return resolve(result);
      } else {
        return reject(new Error(`Function ONE didn't go as planned ...`));
      }
    }, TIMEOUT_MS);
    
  });
}

function twoAsync(resultFormPrev) {
  const TIMEOUT_MS = 1000;
  
  return new Promise((resolve, reject) => { 
    setTimeout(() => {
      const result = `from Two => ${resultFormPrev}`;
      console.log('doing function two => ', result);

      if (result) {
        return resolve(result);
      } else {
        return reject(new Error(`Function TWO didn't go as planned ...`));
      }
    }, TIMEOUT_MS);
  });
}

async function runThemAll() {
 const resultOne = await oneAsync();
 const resultTwo = await twoAsync(resultOne);
}

runThemAll();

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Julian Hansen

@Marek27 - how does your solution differ from the one presented above?