Typescript: Is there a simple way to convert an array of objects of one type to another

Question

So, I have two classes

Item { name: string; desc: string; meta: string}

ViewItem { name: string; desc: string; hidden: boolean; }

I have an array of Item that needs to be converted into an array of ViewItem. Currently, I am looping through the array using for, instantiating ViewItem, assigning values to attributes and pushing it to the second array.

Is there a simple way to achieve this using lambda expressions? (similar to C#) Or is there any other means?

Answer 1

You haven't showed enough of your code, so I'm not sure how you instantiate your classes, but in any case you can use the array map function :

class Item {
    name: string;
    desc: string;
    meta: string
}

class ViewItem {
    name: string;
    desc: string;
    hidden: boolean;

    constructor(item: Item) {
        this.name = item.name;
        this.desc = item.desc;
        this.hidden = false;
    }
}

let arr1: Item[];
let arr2 = arr1.map(item => new ViewItem(item));

( code in playground )

---

Edit

This can be shorter with Object.assign :

constructor(item: Item) {
    Object.assign(this, item);
}

Answer 2

An alternate method is to use Object.keys ,

class Item {
    name: string;
    desc: string;
    meta: string
}

class ViewItem {
    name: string;
    desc: string;
    hidden: boolean;

    // additional properties
    additionalProp: boolean;

    constructor(item: Item) {
        Object.keys(item).forEach((prop) => { this[prop] = item[prop]; });

        // additional properties specific to this class
        this.additionalProp = false;
    }
}

Usage:

let arr1: Item[] = [
    {
        name: "John Doe",
        desc: "blah",
        meta: "blah blah"
    }
];
let arr2: ViewItem[] = arr1.map(item => new ViewItem(item));

Playground link

Answer 3

you can do use something like this.

const newdata = olddata.map((x) => {
        return { id: Number(x.id), label: x.label };
      });

as the converted column will be mapped to the newdata array.