JS: Array.prototype.findIndex

(new in JS: ECMAScript 2015)

similar to JS: Array.prototype.find but return the index of the element found.

if not found, return -1.

const isEven = (x) => (x % 2 === 0 ? true : false);

console.log([7, 3, 4, 2].findIndex(isEven) === 2);

// if not found, return  -1
console.log([1, 3, 5].findIndex(isEven) === -1);