Start Typescript interface temp objects by setting all default property values

Question

Start Typescript interface temp objects by setting all default property values

I am working with an interface called ITreeNode that looks like this -

export interface ITreeNode {
    values: string[];
    key: string;
    isSubHeader?: boolean;
    hours?: number[];
    children?: ITreeNode[];
}

My goal is to create a temporary object based on this interface and then populate its properties sequentially from different sources.

However, when I try to assign a value to the 'key' property of the temporary object, I get an error message stating

cannot assign value to property 'key' of undefined

-

let node: ITreeNode;
node.key = "Something";

How can I resolve this issue?

typescript

Answer 1

Answer №1

It is recommended to initialize this object as a single object literal in order to ensure that the value matches the specified type from the beginning (only mandatory properties need to be assigned):

let newNode:ITreeNode = {
    values: [],
    key: "A"
}

Interactive Example

If creating it as a single object literal is not feasible, you can start with an empty object and use a type assertion, although the value may not fully match the type specification. It's important to ensure that all necessary properties are set during initialization:

let newNode:ITreeNode = { } as ITreeNode
newNode.key = "A"

Live Demo

Answer 2

It is recommended to initialize this object as a single object literal in order to ensure that the value matches the specified type from the beginning (only mandatory properties need to be assigned):

let newNode:ITreeNode = {
    values: [],
    key: "A"
}

Interactive Example

If creating it as a single object literal is not feasible, you can start with an empty object and use a type assertion, although the value may not fully match the type specification. It's important to ensure that all necessary properties are set during initialization:

let newNode:ITreeNode = { } as ITreeNode
newNode.key = "A"

Live Demo

Start Typescript interface temp objects by setting all default property values

Answer №1

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