Question

56

Mongoose - Why we make mongoose.Promise = global.Promise when setting a mongoose module?

rated 0 times [ 58] [ 2] / answers: 1 / hits: 35724 / 6 Years ago, wed, august 15, 2018, 12:00:00

I'm working with Mongoose. I have seen a lot of developers make the following command:

mongoose.Promise = global.Promise;

Then I was curious to see what is the original value of mongoose.Promise . I have entered in my editor the following command:

const mongoose = require(mongoose);



console.log(promise: , mongoose.Promise);

My console returned me :

promise: function Promise() { [native code] }

Okay, so why make the command mongoose.Promise = global.Promise since the Mongoose's promise already returns a native code ? I don't understand the point, if someone can help us to understand, would be great,

Thanks

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answered 6 Years ago diontajm · Accepted Answer

This is legacy code from older examples that isn't needed with Mongoose 5.

Mongoose 4 relied on its own promise implementation, mpromise. mongoose.Promise wasn't necessarily Promise global.

As Mongoose 4 documentation states:

Mongoose 5.0 will use native promises by default (or bluebird,
if native promises are not present) but still
support plugging in your own ES6-compatible promises library. Mongoose 5.0
will not support mpromise.

Though the statement about Bluebird is no longer true; Mongoose 5 dropped the support of Node versions that don't have native promises.

mongoose.Promise = global.Promise;

may still be needed if global.Promise was assigned with another implementation (e.g. Bluebird) after Mongoose was imported, though a better thing would be to assign global.Promise = Bluebird earlier instead.