mongoose.Schema返回的猫鼬是什么？

Question

const mongoose = require('mongoose');

const Schema = mongoose.Schema;

const modelSchema = new Schema({
    a: String,
    b: Date
});

I understand that the first line returns a mongoose. But what exactly does mongoose.Schema return in this code? Why do we need it to write the third line, "const modelSchema = new Schema(...)"?

Answer 1

You do not have to.

It is just a shortcut for saving time writing all the time mongoose.Schema ... the above code:

const mongoose = require('mongoose'); 

const Schema = mongoose.Schema;

const modelSchema = new Schema({
    a: String,
    b: Date
});

Is the equivalent to:

const mongoose = require('mongoose');

const modelSchema = new mongoose.Schema({
    a: String,
    b: Date
});

So to answer your question the line which just gets a reference to the mongoose.Schema is nothing more than a shortcut to save yourself writing extra mongoose. every time :).

The main reason this is often used is since a lot of examples are given with more than one schema defined in a file/example. So to save time and not to repeat the same property path every time it is just referenced with a variable Schema .