TypeScript expandColumnPosition type error

[mehdisolhan]

Hello, i am using this wonderful package in react-typescript. First of all, thank you for that.

I faced an error in expandColumnPosition.
This is my expandRow function;

const expandRow = {
        renderer: (row: any) => (
            <div>
                <p>You can render anything here, also you can add additional data on every row object</p>
                <p>expandRow.renderer callback will pass the origin row object to you</p>
            </div>
        ),
        onlyOneExpanding: true,
        showExpandColumn: true,
        expandColumnPosition: 'right'
 }

It is throwing an error;

I solved this by changing the expandColumnPosition type 'right' | 'left' to string

export interface ExpandRowProps<T, K = number> {
    renderer: (row: T, rowIndex: number) => JSX.Element;
    expanded?: K[];
    onExpand?: (row: T, isExpand: boolean, rowIndex: number, e: SyntheticEvent) => void;
    onExpandAll?: (isExpandAll: boolean, results: T[], e: SyntheticEvent) => void;
    nonExpandable?: K[];
    showExpandColumn?: boolean;
    onlyOneExpanding?: boolean;
    expandByColumnOnly?: boolean;
    expandColumnRenderer?: (props: ExpandColumnRendererProps) => JSX.Element;
    expandHeaderColumnRenderer?: (props: ExpandHeaderColumnRenderer) => JSX.Element;
    //expandColumnPosition?: 'right' | 'left';
    expandColumnPosition?: string;
    className?: string | ((isExpand: boolean, row: T, rowIndex: number) => string);
}

However, i dont understand the error; Type 'string' is not assignable to type '"left" | "right" | undefined'.
Can you fix this?

[mehdisolhan]

Solved.

expandColumnPosition: 'right'

'right' widened itself to type string. However, expandColumnPosition need literal types. To fix it, there is const assertion coming with TypeScript 3.4. I added as const to my code.

expandColumnPosition: 'right' as const

Then 'right' will not turn itself into string.