What is the reason that the Mongoose updateMany() function only functions properly when combined with .then

Question

What is the reason that the Mongoose updateMany() function only functions properly when combined with .then

Currently delving into the intricacies of Mongoose, I am perplexed as to why updateMany() requires a .then() at the end in order to be executed.

For instance, here is the snippet that I'm endeavoring to execute, with the intention of altering the rating of movies from 1992 and 2019:

Movie.updateMany({year: {$in: [1992,2019]}}, {rating: 'M'}).then(data => console.log(data));

The following are the movies in question:

{ "_id" : ObjectId("6282e0d37a9a5a4851d465b1"), "title" : "Elton Pan", "year" : 2013, "score" : 10, "rating" : "M", "__v" : 0 }
{ "_id" : ObjectId("6282e0d37a9a5a4851d465b2"), "title" : "Pon Porom", "year" : 2019, "score" : 0, "rating" : "M", "__v" : 0 }
{ "_id" : ObjectId("6282e0d37a9a5a4851d465b3"), "title" : "The Night", "year" : 1992, "score" : 10, "rating" : "R", "__v" : 0 }

If I omit .then at the end while running the code, no changes occur.

I have observed others utilizing this method without including .then at the end, leading me to question whether my inability to do so stems from the version of Mongoose I'm working with.

To clarify, I am inspecting the outcomes via the Mongo shell instead of trying to retrieve the results within the code itself.

Thank you in advance for your assistance, and pardon my novice inquiry :)

javascript mongodb mongoose

Answer 1

Answer №1

Thanks to @Mats for pointing out that using updateMany without .then won't work as expected, since it returns a Mongoose Query Object instead of the Promise needed to update data. They provide a convenient .then() function for co and async/await, but if you require a fully-fledged promise, use .exec() instead. Check out @Mats' post for more details.

Here's my initial misconception:

I mistakenly believed that calling updateMany would immediately update the data, when in fact, you need to wait for it to complete like any other asynchronous task with a Promise. The .then method allows you to handle the result once the task is finished.

To grasp the concept of Promises in JavaScript, I recommend watching this Youtube Video or reading about it on MDN using the link above. It's an essential aspect of JavaScript programming. Mongoose assumes familiarity with Promises by not explicitly mentioning why they utilize .then in their documentation.

Answer 2

Thanks to @Mats for pointing out that using updateMany without .then won't work as expected, since it returns a Mongoose Query Object instead of the Promise needed to update data. They provide a convenient .then() function for co and async/await, but if you require a fully-fledged promise, use .exec() instead. Check out @Mats' post for more details.

Here's my initial misconception:

I mistakenly believed that calling updateMany would immediately update the data, when in fact, you need to wait for it to complete like any other asynchronous task with a Promise. The .then method allows you to handle the result once the task is finished.

To grasp the concept of Promises in JavaScript, I recommend watching this Youtube Video or reading about it on MDN using the link above. It's an essential aspect of JavaScript programming. Mongoose assumes familiarity with Promises by not explicitly mentioning why they utilize .then in their documentation.

Answer 3

Answer №2

The .then() method is not required for execution in this case. The code runs smoothly with the following syntax:

Movie.updateMany({year: {$in: [1992,2019]}}, {rating: 'M'})

Although the operation is asynchronous, you cannot immediately access the results. This function returns a promise. By using .then(), you can wait for the promise to be fulfilled and receive the result as the first parameter of the callback.

To improve readability and avoid excessive use of .then() chaining, it is advisable to utilize the async...await syntax:

// Encapsulated within an immediately invoked async function
(async () => {
    const data = await Movie.updateMany({year: {$in: [1992,2019]}}, {rating: 'M'})
    console.log(data)
})()

Answer 4

The .then() method is not required for execution in this case. The code runs smoothly with the following syntax:

Movie.updateMany({year: {$in: [1992,2019]}}, {rating: 'M'})

Although the operation is asynchronous, you cannot immediately access the results. This function returns a promise. By using .then(), you can wait for the promise to be fulfilled and receive the result as the first parameter of the callback.

To improve readability and avoid excessive use of .then() chaining, it is advisable to utilize the async...await syntax:

// Encapsulated within an immediately invoked async function
(async () => {
    const data = await Movie.updateMany({year: {$in: [1992,2019]}}, {rating: 'M'})
    console.log(data)
})()

Answer 5

Answer №3

While delving into the intricacies of the .then method, I came across an enlightening explanation from Zarko, a knowledgeable instructor in the (Udemy) course that I am currently engaged in:

In essence, the mongoose query does not inherently generate a genuine promise; instead, it produces a query object that is thenable. Essentially, mongoose facilitates the utilization of callbacks, promises, and async/await syntax when dealing with asynchronous queries. The output of the mongoose query itself manifests as a mongoose 'query' object, which features its own .then method (essentially acting like a bespoke mongoose layer over standard promises). By appending .then to the query object, we initiate the execution of said query. For more information, you can refer to the mongoose documentation here: https://mongoosejs.com/docs/promises.html#queries-are-not-promises

I recommend exploring this informative article for further insights: https://masteringjs.io/tutorials/mongoose/promise

As articulated in the documentation, it is also possible to append the .exec() method after the query to obtain a comprehensive promise - details can be found at Mongoose - What does the exec function do?

Hence, it appears that leveraging either the .then or .exec method is integral in initiating the execution of a query (especially in scenarios where async...await is not utilized). This interpretation is derived from the insights provided by the instructor.

This marks my inaugural post, and I am uncertain whether this content should have been shared as a standalone answer or incorporated within my initial query. Any feedback on this dilemma would be greatly valued. Thank you.

Answer 6

While delving into the intricacies of the .then method, I came across an enlightening explanation from Zarko, a knowledgeable instructor in the (Udemy) course that I am currently engaged in:

In essence, the mongoose query does not inherently generate a genuine promise; instead, it produces a query object that is thenable. Essentially, mongoose facilitates the utilization of callbacks, promises, and async/await syntax when dealing with asynchronous queries. The output of the mongoose query itself manifests as a mongoose 'query' object, which features its own .then method (essentially acting like a bespoke mongoose layer over standard promises). By appending .then to the query object, we initiate the execution of said query. For more information, you can refer to the mongoose documentation here: https://mongoosejs.com/docs/promises.html#queries-are-not-promises

I recommend exploring this informative article for further insights: https://masteringjs.io/tutorials/mongoose/promise

As articulated in the documentation, it is also possible to append the .exec() method after the query to obtain a comprehensive promise - details can be found at Mongoose - What does the exec function do?

Hence, it appears that leveraging either the .then or .exec method is integral in initiating the execution of a query (especially in scenarios where async...await is not utilized). This interpretation is derived from the insights provided by the instructor.

This marks my inaugural post, and I am uncertain whether this content should have been shared as a standalone answer or incorporated within my initial query. Any feedback on this dilemma would be greatly valued. Thank you.

What is the reason that the Mongoose updateMany() function only functions properly when combined with .then

Answer №1

Answer №2

Answer №3

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