Javascript not waiting for function return when using console.log statement

Question

Javascript not waiting for function return when using console.log statement

I am facing an issue where I need to set a variable x to the result obtained from the showData function. Below is my code snippet:

app.post("/view/show", (req,res) => {
    let x = showData(req.body.custmerName);
    console.log(x);
}

Here's how the showData function looks like:

const showData = (custName) => {
    const customer = mongoose.model(custName ,collectionSchema,custName);
    customer.find( (error,data) => {
        if (error){
            console.log(error);
        }else{
            return data;  
        }
    });
}

Despite successfully fetching data from the database and logging it using console.log(data), when I tried to log the value of x, it displayed undefined. This seems to happen because the console.log(x) does not wait for the execution of showData() due to JavaScript's synchronous nature. What can I do to ensure that the value returned by the function is properly logged instead of being shown as undefined?

javascript express async-await async.js awaitility

Answer 1

Answer №1

Utilizing async/await or callbacks is the recommended approach when dealing with asynchronous functions.

app.post("/view/show", (req,res) => {
  showData(req.body.custmerName, (err, res) => {
    const x = res;
    console.log(x);
  });
});

const showData = (custName, callback) => {
  const customer = mongoose.model(custName ,collectionSchema,custName);
  customer.find(callback);
}

Answer 2

Utilizing async/await or callbacks is the recommended approach when dealing with asynchronous functions.

app.post("/view/show", (req,res) => {
  showData(req.body.custmerName, (err, res) => {
    const x = res;
    console.log(x);
  });
});

const showData = (custName, callback) => {
  const customer = mongoose.model(custName ,collectionSchema,custName);
  customer.find(callback);
}

Answer 3

Answer №2

I am not familiar with using Mongoose, but upon reviewing the documentation, it appears that there is no direct callback function available for the find method.

You can try passing an empty query object as well:

customer.find({}, (error,data) => {
    if (error) {
        console.log(error);
    } else {
        return data;  
    }
});

According to the documentation:

// find all documents
await MyModel.find({});

// find all documents named john and at least 18
await MyModel.find({ name: 'john', age: { $gte: 18 } }).exec();

// executes, passing results to callback
MyModel.find({ name: 'john', age: { $gte: 18 }}, function (err, docs) {});

// executes, name LIKE john and only selecting the "name" and "friends" fields
await MyModel.find({ name: /john/i }, 'name friends').exec();

// passing options
await MyModel.find({ name: /john/i }, null, { skip: 10 }).exec();

Answer 4

I am not familiar with using Mongoose, but upon reviewing the documentation, it appears that there is no direct callback function available for the find method.

You can try passing an empty query object as well:

customer.find({}, (error,data) => {
    if (error) {
        console.log(error);
    } else {
        return data;  
    }
});

According to the documentation:

// find all documents
await MyModel.find({});

// find all documents named john and at least 18
await MyModel.find({ name: 'john', age: { $gte: 18 } }).exec();

// executes, passing results to callback
MyModel.find({ name: 'john', age: { $gte: 18 }}, function (err, docs) {});

// executes, name LIKE john and only selecting the "name" and "friends" fields
await MyModel.find({ name: /john/i }, 'name friends').exec();

// passing options
await MyModel.find({ name: /john/i }, null, { skip: 10 }).exec();

Answer 5

Answer №3

In order to accomplish this task, you will require an asynchronous function. Follow these steps:

app.post("/view/show", async(req,res) => {
    let display = await fetchCustomerData(req.body.custmerName);
    console.log(display);
}

Answer 6

In order to accomplish this task, you will require an asynchronous function. Follow these steps:

app.post("/view/show", async(req,res) => {
    let display = await fetchCustomerData(req.body.custmerName);
    console.log(display);
}

Javascript not waiting for function return when using console.log statement

Answer №1

Answer №2

Answer №3

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