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Shilpa
Published in : 2022-03-06

Way to bypass a value if it is not existing in Async data fetch iterations

Node JS & Mongo

I wrote a script with node.js, which will invoke a function on a blockchain returning some output results. I have to collect the first 6k values (let's say 0 to 5.999K values).

let blockURIArr = [];
   for (let tknId= 0; tknId< 5999; tknId++) {
    let output = await BackendServices.tknBlockURI(tknId);
     console.log(output );
     blockURIArr .push(output );

     if (output = '') {
       continue;
     }
  }

Somehow, a few values do not exist and the loop is stopped when it encountered such issues. How should I prevent it?

Comments

Rakshit Date : 2022-03-06

Best answers

34

Best answers

34

Why don't you use the “try-catch” block? It will fix your problem when iteration doesn't have any values.

Below code will be continued your loop throughout your condition used in for loop from stopping the iterations.

for (...) { // Add your for loop
  try{ // Add try block for your code
        let output = await BackendServices.tknBlockURI(tknId);
     	console.log(output);
     	blockURIArr.push(output);
  }catch(e){ //Handle exceptions when it throws exception.
    console.log(e); //Console iteration number which was failed. You can see the failed ones here.
  }
}

Also when you compare with IF CONDITION, please use `==` or  `===`, not the =

Your code contains =  for comparison, That's why it is assigning null value and fails from iterating throughout loops.

 if (output = '') {
    continue;
 }

Hope this will answer your question and help to fix your code fault.

Shilpa Date : 2022-03-06

Best answers

10

Best answers

10

Thank you for putting my attention to if condition, I thought  - I put ==  only. This solution works!

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