No index signature with a parameter of type 'string' was found on type 'Query'

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I'm using accesscontrol npm package for RBAC(role based access control) in my api this is my code for checking if the user has permission on resource or not:

export const checkUserPermission = async (
  req: Request,      
  role: string,
  resource: string,
  action = 'readAny'
) => {
  const userRole = await Role.findOne({ name: role });
  if (!userRole) return sendErrorResponse(res, 400, 'Role is not exists.');
  const grantLists = await getPermissionsBasedOnRole(role);
  if (grantLists.length === 0)
    return sendErrorResponse(
      res,
      401,
      'Permission is not assigned for this role. please assign and try again.'
    );
  const ac = new AccessControl(grantLists);
  const permission = ac.can(role)[action](resource);
  if (!permission.granted)
    return sendErrorResponse(
      res,
      500,
      'You have no permission to perform this action.'
    );
};

In nodejs this function is working just fine. but when I try it with typescript I'm getting this error:

Element implicitly has an 'any' type because expression of type 'string' can't be used to index type 'Query'.
  No index signature with a parameter of type 'string' was found on type 'Query'.

from

  const permission = ac.can(role)[action](resource);
role-based-access-control express typescript node.js
1 Answers

I found the solution after reading the typescript docs specifically https://www.typescriptlang.org/docs/handbook/2/everyday-types.html#type-aliases, union, and string literal.

I just defined the types of the action using string-literal, union, and types-aliases in typescript and annotated the action type to this and everything is just working fine:

type ActionType = 'createAny' | 'updateAny' | 'deleteAny' | 'readAny';

Below is the full source code:

type ActionType = 'createAny' | 'updateAny' | 'deleteAny' | 'readAny';

export const checkUserPermission = async (
  res: Response,
  role: string,
  resource: string,
  action: ActionType
) => {
  const userRole = await Role.findOne({ name: role });
  if (!userRole) return sendErrorResponse(res, 401, 'Role is not exists.');
  const grantLists = await getPermissionsBasedOnRole(role);
  if (grantLists.length === 0)
    return sendErrorResponse(
      res,
      401,
      'Permission is not assigned for this role. please assign and try again.'
    );
  const ac = new AccessControl(grantLists);
  const permission = ac.can(role)[action](resource);
  if (!permission.granted)
    return sendErrorResponse(
      res,
      500,
      'You have no permission to perform this action.'
    );
};
H_POYA0
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