JS。 将嵌套循环替换为标准数组 API

Question

I had a case with comparing two arrays to getting user access to page:

let permitted = false;
const { authorities } = route.data;
const { roles } = user;
for (const role of roles) {
  for (const authority of authorities) {
    if (role.systemName === authority) {
      permitted = true;
      break;
    }
  }
}

User has an array of roles and each role has field systemName is the value of an enum UserType .

authorities is array of UserType values directly.

export enum UserType {
  User = 'USER_ROLE',
  Admin = 'ADMIN_ROLE',
}

How to refactor this nested loops with standard array API like some(...) , indexOf(...) of JavaScript?

Answer 1

While you can do it with a nested .some ( O(n ^ 2) ), it would be more efficient to make a Set of one of the collections first, then use .some on the other ( O(n) ):

const { authorities } = route.data;
const { roles } = user;
const systemNames = new Set(roles.map(({ systemName }) => systemName));
const permitted = authorities.some(
  authority => systemNames.has(authority)
);