How to correctly type the parameter?

Question

typescript

Good day to all! I am making a universal function to change a boolean value in an object that is part of an array.

export type TodoListArrayType = Array<{
    id: number,
    subtitle: string,
    important: boolean,
    done: boolean,
}>

const generalToggle = (arr: TodoListArrayType, id: number, propertyName: any) => {
        const idx = arr.findIndex((item) => item.id === id);
        const oldItem = arr[idx];
        const value = !oldItem.propertyName;

        const item = {...arr[idx], [propertyName]: value};
        return [
            ...arr.slice(0, idx),
            item,
            ...arr.slice(idx + 1)
        ];
    };

An error occurs with the propertyName value.

TS2339: Property 'propertyName' does not exist on type '{ id: number; subtitle:string; important: boolean; done: boolean; }'.

I know for sure that propertyName will be either important or done from the type TodoListArrayType . But I can't find any information (or understand it correctly) in any way how to convey this information in the code. Please tell me how to correctly pass the type for propertyName.

Answer 1

interface TodoItem {
    id: number
    subtitle: string
    important: boolean
    done: boolean
}

const generalToggle = (arr: TodoItem[], id: number, propertyName: keyof TodoItem) => {
        const idx = arr.findIndex((item) => item.id === id);
        const oldItem = arr[idx];
        const value = !oldItem[propertyName];

        const item = {...arr[idx], [propertyName]: value};
        return [
            ...arr.slice(0, idx),
            item,
            ...arr.slice(idx + 1)
        ];
    };

Better yet, keep the TODO object by key (for mutations) and a separate list of IDs (for rendering the list) so that O(n) is not driven for each change.

Answer 2

Everything swears correctly, because the `propertyName` field is really not in TodoListArrayType and you have an error in your code
. You need to address it as `oldItem[proprtyName]`. But it is not a fact that the linter will not swear at this