prefer-ts-extras-array-find-last

Prefer arrayFindLast from ts-extras over array.findLast(...).

arrayFindLast(...) improves predicate inference and value narrowing in typed arrays.

Targeted pattern scope

This rule focuses on direct array.findLast(predicate) calls that can be migrated to arrayFindLast(array, predicate) with deterministic fixes.

array.findLast(predicate) call sites that can use arrayFindLast(array, predicate).

Alias indirection, wrapper helpers, and non-canonical call shapes are excluded to keep arrayFindLast(array, predicate) migrations safe.

What this rule reports

This rule reports array.findLast(predicate) call sites when arrayFindLast(array, predicate) is the intended replacement.

array.findLast(predicate) call sites that can use arrayFindLast(array, predicate).

Why this rule exists

arrayFindLast makes reverse-direction predicate lookups explicit and keeps them aligned with the ts-extras helper style.

Reverse scans are easier to spot during code review.
Call signatures stay consistent with arrayFind / arrayFindLastIndex.
Utility code that depends on "latest match" is easier to audit.

❌ Incorrect

const monitor = monitors.findLast((entry) => entry.id === targetId);

✅ Correct

const monitor = arrayFindLast(monitors, (entry) => entry.id === targetId);

Behavior and migration notes

Runtime behavior matches native Array.prototype.findLast.
Search direction remains right-to-left.
Result is the matching element, or undefined if no match exists.

Additional examples

❌ Incorrect — Additional example

const latest = events.findLast((entry) => entry.type === "login");

✅ Correct — Additional example

const latest = arrayFindLast(events, (entry) => entry.type === "login");

✅ Correct — Repository-wide usage

const trailingError = arrayFindLast(logs, (entry) => entry.level === "error");

ESLint flat config example

import typefest from "eslint-plugin-typefest";

export default [
    {
        plugins: { typefest },
        rules: {
            "typefest/prefer-ts-extras-array-find-last": "error",
        },
    },
];

When not to use it

Disable this rule if your team intentionally uses native .findLast() everywhere.

Package documentation

ts-extras package documentation:

ts-extras@0.17.x does not currently expose arrayFindLast in its published API, so there is no canonical source/*.ts link for this helper yet.

Reference links:

Rule catalog ID: R004

prefer-ts-extras-array-find-last

Targeted pattern scope

What this rule reports

Why this rule exists

❌ Incorrect

✅ Correct

Behavior and migration notes

Additional examples

❌ Incorrect — Additional example

✅ Correct — Additional example

✅ Correct — Repository-wide usage

ESLint flat config example

When not to use it

Package documentation

Further reading

Adoption resources

Targeted pattern scope​

What this rule reports​

Why this rule exists​

❌ Incorrect​

✅ Correct​

Behavior and migration notes​

Additional examples​

❌ Incorrect — Additional example​

✅ Correct — Additional example​

✅ Correct — Repository-wide usage​

ESLint flat config example​

When not to use it​

Package documentation​

Further reading​

Adoption resources​

Targeted pattern scope

What this rule reports

Why this rule exists

❌ Incorrect

✅ Correct

Behavior and migration notes

Additional examples

❌ Incorrect — Additional example

✅ Correct — Additional example

✅ Correct — Repository-wide usage

ESLint flat config example

When not to use it

Package documentation

Further reading

Adoption resources