Strings array to object. Element implicitly has an 'any' type because expression of type 'string' can't be used to index type '{}'

Issue

Hi I ave a code like this:

export type Options = Record<string, string>

export type CheckboxValue<T extends Options> = Partial<
    Record<keyof T, boolean>
>

export type Checkbox<T extends Options> = {
    value: CheckboxValue<T>
}
export function Checkbox<T extends Options>({
    value,
}: Checkbox<T>) {
    return value
}

export type FilterProps<T extends Options> = {
    options: T
    value: string[]
}

export function Filter<T extends Options>(
    props: FilterProps<T>,
) {
    const {  value = [] } = props

    const mappedValue = (() => {
        const contextValue: string[] = value

        const result = {}

        for (const item of contextValue) {
            /*
             * Element implicitly has an 'any' type because expression of type 'string' can't be used to index type '{}'.
             *   No index signature with a parameter of type 'string' was found on type '{}'.(7053)
             */
            result[item] = true
        }

        return result
    })()

    return Checkbox({value: mappedValue})
}

Why does this happen and how to fix it?

ts playground

Solution

You could use the index signature:

const result: { [key: string]: boolean } = {}

As to why it happens if I'd explain it most likely it wouldn't be accurate. Maybe TS docs could help you: https://www.typescriptlang.org/docs/handbook/2/objects.html#index-signatures

Update: This old SO thread could also be useful: How do I prevent the error "Index signature of object type implicitly has an 'any' type" when compiling typescript with noImplicitAny flag enabled?

Answered By - Kari F.