Returns the index of the first element in the array that satisfies the provided testing function. Otherwise None is returned.
None
An array
A predicate function.
Optional
If provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.
undefined
The index of the first item that matches the predicate, or None if no item matches.
Returns the index of the first element in the array that satisfies the provided testing function. Otherwise
None
is returned.