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replace ​

Problem ​

You need to swap one item in an array with a new value without mutating the original — for example updating a single record in an immutable list.

Solution ​

Use replace(array, predicate, value) to return a new array with the first matching item replaced.

ts
import { replace } from '@vielzeug/arsenal';

const users = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' },
];

replace(users, (u) => u.id === 2, { id: 2, name: 'Robert' });
// [{ id: 1, name: 'Alice' }, { id: 2, name: 'Robert' }]

Pitfalls ​

  • Only the first matching item is replaced. Use filterMap or map for replacing all matches.
  • Returns the original array unchanged if no item matches.