JavaScript findIndex: Locate the First Record Matching a Condition

The task

Locate the first available camera record and then search for an unavailable category. Compare the predicate search with indexOf on a newly constructed object.

Runnable Node 22 example

const assert = require('node:assert/strict');

const equipment = [{kind: 'camera', available: true}, {kind: 'tripod', available: true}, {kind: 'camera', available: true}];
const first = equipment.findIndex(item => item.kind === 'camera' && item.available);
assert.equal(first, 0);
assert.equal(equipment.findIndex(item => item.kind === 'microphone'), -1);
assert.equal(equipment.indexOf({kind: 'camera', available: true}), -1);
assert.equal(equipment[first], equipment[0]);
console.log(`first=${first}; kind=${equipment[first].kind}`);

Expected output and explanation

Two cameras satisfy the condition, but findIndex stops at the first and returns zero. The missing microphone produces −1. A truthiness test would mishandle both values, so compare against −1 before reading equipment[index].

The indexOf call does not inspect the new object’s fields for equality; it searches for that exact reference and fails. findIndex makes the record-level match rule explicit without changing array membership or cloning the matching item.

Pitfall to check

If you need every matching record, filter expresses a different task. If you only need the first matching value, find avoids a separate lookup. Choose the result shape the caller actually needs.