`Array.prototype.findIndex()`

Returns the index of the first element that satisfies the testing function.

Since ES2015 Spec ↗

Syntax

arr.findIndex(callback, thisArg)

Name	Type	Required	Description
`callback`	`Function`	Yes	Predicate called with (element, index, array). Return truthy to select the element.
`thisArg`	`any`	No	Value to use as `this` when executing the callback.

number — The index of the first matching element, or -1 if none match.

const nums = [5, 12, 8, 130, 44];
console.log(nums.findIndex(n => n > 10));

Output

console.log([1, 2, 3].findIndex(n => n > 9));

Output

-1

Returns -1 when nothing matches. Use `find` to get the value instead of the index, or `indexOf` for a strict equality search.