Is it possible to add a default value to the level property?

[young sparrow]

hello, I wonder if there is a way to set a default value to the level property:

export interface NavItemProps<T> {
    id: string;
    title: string;
    path: string;
    metaData?: NavMetaData;
    subNav?: NavItemProps<T>[];
}

export interface NavMetaData {
    level: string;
    fileType: string;
}

// how I am using the Interface
const SideNavMenu = ({items}:{ items: NavItemProps<string>[]}) => {
    // ....
};

[vivid current]

no, it's not possible
at least not when using types or interfaces

types or interfaces don't exist at runtime, so they can't hold values

they are only used at compile-time to ensure your code is correct and you are not trying to access a property that does not exist

if you want to provide a default value, you could try merging your object with another object holding default values

also, a few things

instead of writing { items }: { items: NavItemProps<string>[] }, you could write items: NavItemProps<string>[]

[obtuse wolf]

ascor8522#0

Playground Link

Preview:```ts
export interface NavItemProps<T> {
id: string;
title: string;
path: string;
metaData?: NavMetaData;
subNav?: NavItemProps<T>[];
}

export interface NavMetaData {
level: string;
fileType: string;
}

// how I am using the Interface
...```

You can choose specific lines to embed by selecting them before copying the link.

[vivid current]

!ts

[obtuse wolf]

export interface NavItemProps<T> {
    id: string;
    title: string;
    path: string;
    metaData?: NavMetaData;
    subNav?: NavItemProps<T>[];
}

export interface NavMetaData {
    level: string;
    fileType: string;
}

// how I am using the Interface
const SideNavMenu = (items: NavItemProps<string>[]) => {
    items = items
        .map(item => ({
            ...item,
            metaData: {
                level: item.metaData?.level ?? "default level value",
                fileType: item.metaData?.level ?? "default fileType value",
            },
        }));
};

[vivid current]

this way you can provide a default value for each item's level and fileType

tho it's a big verbose

it's usually better to give a default value right after creating the object or when trying to access the property

@young sparrow

[young sparrow]

@vivid current awesome sir! thanks a lot for this great explanation!

[long vault]

!close