Question 215743 in Javascript Question posted in
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Javascript – Cannot read properties of undefined (reading 'then'). Promise.resolve() won't work

For some reason my promise is not being resolved on time. I can’t understand why, as my functions aren’t asynchronous.

What I’m trying to achieve is to go through an entire array and resolve a promise only after all the elements have been validated (If necessary)

So whenever the resolving conditions are met, I call promiseHelper = Promise.resolve(value). But for some reason I’m getting: Cannot read properties of undefined (reading 'then') even though promiseHelper.then is written after the recursive function, which means the helper should be resolved before the then statement.

My question is: Why does the variable come to that part of the code without being a promise? And if possible, what’s a better approach to achieve such functionality

Here’s the code:

const cart = req.body.items; //Array of items
let promiseHelper;           
function recursiveCheck(cartIndex){
    let pieceOutOfStock = Piece.find({nombre: cart[cartIndex].name, cantidad: {$gte:cart[cartIndex].amount}});
    pieceOutOfStock.then(response =>{
        if (!response.length){  //If nothing on the query, resolve as false
                console.log("not enough:", element.amount, response.length);
                promiseHelper = Promise.resolve(false);
                return false;
                
        }
        else{
               if(cart.length > cartIndex+1){ //If something on the query and items left, validate next item
                    recursiveCheck(cartIndex+1);
               }  
               else{ //if last item, resolve as true
                    promiseHelper = Promise.resolve(true);
                    return true;
               }         
            }
    })
}

function getStock(){
   return new Promise (resolve =>{
          recursiveCheck(0);
          promiseHelper.then(response =>{
              if(!response){
                    resolve("reject")
              }
              else{
                    resolve("All good")
              }
          })
            
  })
}

    getStock().then(async response =>{
    //do some stuff

    }

Any help is appreciated

Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    Update:

    I found a work around for my code (still don't know the answer to the very first question tho)

    response(resolve) allows me send my info to query. And finally the deepest else statement acknowledges the end of the loop, so I just started my final process in there.

    Thanks all :)

        function recursiveCheck(cartIndex){
        return new Promise (resolve =>{
        let pieceOutOfStock = Piece.find({nombre: cart[cartIndex].name, cantidad: {$lte: cart[cartIndex].amount}});
        pieceOutOfStock.then(response =>{
            resolve(response);
        })
    }).then(query =>{
        if(!query.length){
            res.json({url: "http://localhost:3000/stockerror"});
            return query;
        }
        else{
            if(cart.length > cartIndex+1){
                return recursiveCheck(cartIndex+1);
            }
            else{
                stripeProcess();
            }
        }
    })
    }
    recursiveCheck(0);

  2. 0

    await until u get the stock

    async function recursiveCheck(cartIndex){
    let pieceOutOfStock = await Piece.find({nombre: cart[cartIndex].name, cantidad: {$gte:cart[cartIndex].amount}});
    pieceOutOfStock.then(response =>{
        if (!response.length){  //If nothing on the query, resolve as false
                console.log("not enough:", element.amount, response.length);
                promiseHelper = Promise.resolve(false);
                return false;
                
        }
        else{
               if(cart.length > cartIndex+1){ //If something on the query and items left, validate next item
                    recursiveCheck(cartIndex+1);
               }  
               else{ //if last item, resolve as true
                    promiseHelper = Promise.resolve(true);
                    return true;
               }         
            }
    })
}
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