Question 297260 in Javascript Question posted in
A very good W3school tutorial can be found here.

Javascript – check value inside array or not with async

If I need to check value inside array or not, then I will use includes,

let orig_arr = [1,2,3];
let input = 1;

if (orig_arr.includes(input)) {
  // ...
}

If wanna do async way then user for await loop

for await (let el of orig_arr) {
  if (el == input) {
    // ...
  }
}

But because it has more wrap, so I will use flag like below, or just write a lib calling it with async

let flag = false;
for await (let el of orig_arr) {
  if (el == input) {
    flag = true;
  }
}
if (flag) {
  // ...
}

lib_array_include_async = (reqArray, reqItem) => {
   return new Promise((resolve, reject) => {
    (async () => {
      // ...
    })();
  });
};
// await lib_array_include_async(reqArray, reqItem)

Is there any shorter way , original javascript function, syntax can do same thing to check value inside array or not with async ?
like for let loop just add await simply become async

Tags:

2

Answers


  1. 0

    You could get an async iterator for an array.
    You have to wait the async iterators helper some() otherwise implement it yourself.
    https://github.com/tc39/proposal-async-iterator-helpers

    A polyfil could be like that:

    const AsyncIteratorPrototype = Object.getPrototypeOf(
  Object.getPrototypeOf(Object.getPrototypeOf((async function* () {})())),
);

AsyncIteratorPrototype.some = async function(cb){
  for await(const item of this){
    if(await cb(item)) return true;
  }
  return false
};

async function* arrayToAsync(arr){
  for(const item of arr){
    yield item;
  }
}


arrayToAsync([1,2,3,4,5]).some(num => num === 5).then(out => console.log(out));
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  2. 0

    I guess the OP could want to check an array item existence with async code item-by-item.
    For that you either create a custom promise queue or use for await again.
    If your item check callback doesn’t use a shared state between invocations you could use just
    Promise.any to resolve all callbacks simultaneously:

    const arr = [1,2,3,4,5];


Promise.any(arr.map(async item => {
   
   await new Promise(resolve => setTimeout(resolve, Math.random()*300));
   
   if(item === 5){
    return true;
   }
   
   throw new Error('not equal');
  
})).then(() => console.log('found')).catch(() => console.error('not found'));
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