Not catching an error from async await despite using try catch blocks

Question

I'm using a loop to get all whatsapp messages associated with given numbers, using whatsappweb-js. When there is error in this line "let chat = await client.getChatById(nums[i])" I'm not able to catch it , instead I get an error refering to the next line stating that "chat is not defined"! if I remove try catch I don't get any errors but the node js application just stop responding note: client.getChatById(id) return a promise containing chat object.

function fetch(nums) {
    for (let i = 0; i < nums.length; i++) {
        try {
            let chat = await client.getChatById(nums[i])
        } catch (err) {
            console.log(err)
        };
    }
    return msgs = await chat.fetchMessages();
}

You're declaring `chat` inside the try so it's not available outside due to scope. — pilchard, Dec 30 '21 at 16:44
You need to add async, as in `async function fetch(nums)`, but that may not be the only issue — Andy Ray, Dec 30 '21 at 16:45
@AndyRay That must be a copying error (like the missing close brace), because otherwise it wouldn't even run. — Barmar, Dec 30 '21 at 16:45
though with a return inside the loop it's only going to run once — pilchard, Dec 30 '21 at 16:46

score 1 · Answer 1 · answered Dec 30 '21 at 16:50

1

The code that uses chat needs to be inside the try block. This is needed for scoping reasons, and also because it doesn't make sense to use chat if the call failed.

Also, you shouldn't have return inside the loop, since you want to collect the results from all the chats. Declare an array to hold them, add to the array in the loop, then return at the end.

async function fetch(nums) {
  let msgs = [];
  for (let i = 0; i < nums.length; i++) {
    try {
      let chat = await client.getChatById(nums[i]);
      msgs = msgs.concat(await chat.fetchMessages());
    } catch (err) {
      console.log(`while fetching ${nums[i]}`, err)
    };
  }
  return msgs;
}

answered Dec 30 '21 at 16:50

Barmar

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Better answer than mine :) - I couldn't figure out how to explain it properly. – Ricky Dec 30 '21 at 16:52
Thank you ,a curly bracket got lost , I'm in fact returining msgs outside loop. – Schwan Abdulkareem Dec 30 '21 at 17:04
1

That doesn't make sense, either, because then `chat` only contains the result from the last iteration of the loop. – Barmar Dec 30 '21 at 17:04

score 0 · Answer 2 · answered Dec 30 '21 at 16:51

You need to move the return:

    function fetch(nums) {
  for (let i = 0; i < nums.length; i++) {
    try {
      let chat = await client.getChatById(nums[i])
      return msgs = await chat.fetchMessages();
    } catch (err) {
      console.log(err)
    }; 
  }

Your putting your chat variable outside the try/catch, so it wouldn't know what the variable is.

Not catching an error from async await despite using try catch blocks

2 Answers2