The latest JavaScript specification standardizes a well-balanced and thoughtful set of features, including the built-in global Iterator, new Set methods, improvements to regular expressions, and more.

The findIndex() method returns the index of the first element in the array that satisfies the provided callback function. Otherwise, it returns -1, indicating that no element passed the test.

Javascript reduce method parameters The reduce method accepts two arguments: a reducer function for the array that is used as a callback, and an optional initialValue argument.