Is there a Deconstruct Mongo Response to DTO short cut? - mongodb

Question

If I have a table in a mongoDB with five properties and I only want to return four of them and none of the mongo added info such as v1 I can map the reposne to a dto like so,
const product = await this.productModel.findById(productId).exec()
return { id: product.id, title: product.title }
Is there a deconstruct shortcut for the return, to extract every field from an interface (Product) from the product response, to save typing each property out ? If for example im retunring 127 properties from a table of entires with 140.
interface Product {
id: string
title: string
...
}

Answer 1

Unfortunately no, typescript interfaces do not really exist when your program compiles
Interface is a structure that defines the contract in your application. It defines the syntax for classes to follow. Classes that are derived from an interface must follow the structure provided by their interface.
The TypeScript compiler does not convert interface to JavaScript. It
uses interface for type checking. This is also known as "duck typing"
or "structural subtyping".
So, you can't really read interface fields and then write some logic (you can maybe achieve this through reflection but it's a bad practice)
An alternative is to explicitly define what fields are to include/or exclude from your object
Suppose that I have an object with this interface:
interface Foo {
field1: string;
field2: string;
field3: string;
.....
field140: string;
}
What you can do here is to define what properties you want to exclude (you take the exclude approach here since you are returning 127 fields of 140)
// This isn't an implementation with mongoose (if you are using it),
// it's just to give you the idea
const FIELDS_TO_EXCLUDE = ["field128", "field129", "field130", ..., "field140"];
productModel.toDTO(){
const documentData = this;
FIELDS_TO_EXCLUDE.forEach(x => delete documentData[x]);
return documentData;
}
In this way, when you will execute the toDTO function your manipulate itself excluding (or including) the fields you want