Transforming "larger" items into "smaller" items using Typescript

I am experiencing challenges when trying to assign larger objects into smaller ones. To illustrate this issue, I will provide a simple example:

Let's say I have defined the Typescript interface:

export interface CrewMember {
   name: string;
   organizing_function?: string;
 }

Now, I fetch an array of objects from a database that looks like this:

[{
 id: "someID",
 name: "Jack"
},{
 id: "someOtherID",
 name: "Jipp",
 organizing_function: "Being good at stuff"
}]

My goal is to create an Array< CrewMember > to store the objects retrieved from the database. However, the objects from the database have an "ID" property that the "CrewMember" interface does not have. Therefore, I cannot simply assign them due to Typecript raising compatibility errors.

Initially, I attempted the following approach:

let crewmember : CrewMember = {
 name: database[0].name,
 organizing_function: database[0].organizing_function
};

However, this method is (1) laborious, especially when dealing with more extensive object types, and (2) complex because the organizing_function is optional. Consequently, I would need to implement numerous "IF" conditions to determine the presence of properties in the database object and assign them correctly.

What is the most efficient way to convert an object with unnecessary properties into another object with numerous optional properties in Typescript?

Any guidance on this matter would be greatly appreciated. Thank you.

Answer №1

While Typescript is primarily a compile-time tool, it's important to remember that everything ultimately boils down to javascript, with no inherent typing present.

When it comes to casting in Typescript, it differs from casting in languages like Java, where a runtime check is performed. In Typescript, you have the flexibility to write code like:

const a: { prop: string } = (4 as any)

This code will not cause any issues. Even though it may not conform to the expected { prop: string } structure, the casting itself will still be successful.

For instance, if you have a javascript object named data with a type of

{ id: string; name: string; organizing_function: string}[]
, you can simple write:

const members: CrewMember[] = data;

And you're good to go.

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