findIndex() function

Returns the index of the first element of Iterable/AsyncIterable which matches f, or -1 if no element matches.

Signature:

declare function findIndex<T extends readonly []>(f: Arrow, iterable: T): -1;

Example

const arr = [{a:1}, {a:2}, {a:3}]
findIndex((obj) =>  obj.a === 1, arr); // 0
findIndex((obj) =>  obj.a === 2, arr); // 1
findIndex((obj) =>  obj.a === 4, arr); // -1

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