formatting response object - sequelize ORM. async function inside a loop

Question

exports.getAllProducts = async () => {
    const query = "some mysql query"; 
    products = await db.sequelize.query(query, { type: sequelize.QueryTypes.SELECT });
    var result = new Array();
    products.forEach(product => {
        result.push({
            //'isLiked': helpers.isLiked(req.user.id, product.productId),
            'productId': product.productId,
            'product_price': product.product_price,
            'product_name': product.product_name,
            'shop_name': product.shop_name,
            'shop_picture': product.shop_picture,
            'product_image': product.product_image,
            'num_comments': product.num_comments,
        })
    });
    return result;
}

In my Node.js project I am using Sequelize as an ORM. But sometimes I want to use raw queries but I have got this issue to fix. Once the query is done I am looping through it using a forEach function. For each iteration I want to call another async function (check the commented code) and put the returned value in isLiked as value and once it does all looping - send back the array as a response. NOTE: the async function is another DB function which checks the DB for some value.

The problem Here I guess is since I am calling an async function and the loop doesn't wait until the function goes and gets result back and put in the value.

mcranston18 · Accepted Answer · 2018-11-26 16:03:23Z

1

In your case, if you want to perform an asyncronous operation in sequence, you cannot use a forEach loop. Instead, you should use for ... of which will allow you to use async/await properly:

exports.getAllProducts = async () => {
  const query = 'some mysql query';

  const products = await db.sequelize.query(query, {
    type: sequelize.QueryTypes.SELECT
  });
  var result = new Array();

  for (product of products) {
    const isLiked = await helpers.isLiked(req.user.id, product.productId)
    result.push({
      'isLiked': isLiked,
      productId: product.productId,
      product_price: product.product_price,
      product_name: product.product_name,
      shop_name: product.shop_name,
      shop_picture: product.shop_picture,
      product_image: product.product_image,
      num_comments: product.num_comments
    });
  }

  return result;
};

edited Nov 26, 2018 at 16:03

answered Nov 18, 2018 at 16:48

mcranston18

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3 Comments

bee321 Over a year ago

hi, that works perfectly well. however if use this same async helper functions in another query and from the front-end if i want to call both the api endpoints at the same time. it blows up. any solution for this?

bee321 Over a year ago

now i ran into this problem and i am very much desperate in solving this one. stackoverflow.com/questions/53483697/…

mcranston18 Over a year ago

@bee321 I'll take a look. If this answer is correct for the question, could you accept it?

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