How to use Promise with nested foreach

Question

I am finding all users wallets in nested foreach loop but i am unable to figure out where to use resolve() for return callback,

function genwallets() {
    return new Promise((resolve, reject) => {
    var i = 0;
    try {
        db.users.findAll({}).then((users)=>{
            db.supportedTokens.findAll({}).then((tokens)=>{ 
                users.forEach(function(user) {
                    tokens.forEach(function(token) {
                    db.wallets.findOne({where:{userId: user['id'], supportedTokenId: token['id']}}).then((wallet)=>{
                        console.log(JSON.stringify(wallet));
                    })
                    });
                });
            })
        });

    } catch (err) {
        console.log(err);
    }
});
}

did you check this? https://stackoverflow.com/questions/53892863/how-to-wait-a-promise-inside-a-foreach-loop — bakar_dev, Mar 16 '20 at 12:45
If you are using `Promise` then why are you creating a [callback hell](http://callbackhell.com/) scenario? — palaѕн, Mar 16 '20 at 12:49

score 1 · Accepted Answer · answered Mar 16 '20 at 12:47

forEach doesn't work with promises. either use for...of or Promise.all something like this

function genwallets() {
  return new Promise((resolve, reject) => {
    var i = 0;
    try {
      db.users.findAll({}).then(users => {
        db.supportedTokens.findAll({}).then(tokens => {
          for(const user of users) {
            for(const token of tokens) {
              db.wallets
                .findOne({
                  where: { userId: user["id"], supportedTokenId: token["id"] }
                })
                .then(wallet => {
                  console.log(JSON.stringify(wallet));
                });
            }
          }
        });
      });
    } catch (err) {
      console.log(err);
    }
  });
}

by the way you dont need to wrap it in promise.

You could simplify this using async/await

async function genwallets() {
  const users = await db.users.findAll({});
  const tokens = await db.supportedTokens.findAll({});

  for(const user of users) {
    for(const token of tokens) {
      const wallet = await db.wallets
        .findOne({
          where: { userId: user["id"], supportedTokenId: token["id"] }
        });
    }
  }
}

How to use Promise with nested foreach

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