Javascript - flatMap method over array - (flatMap is not a function)

Question

According to the Mozilla Developer Website:

The flatMap() method first maps each element using a mapping function, then flattens the result into a new array. It

Answer 1

It means you're using a web browser or other development environment that does not support Array.prototype.flatMap (currently Edge and IE have no support). CanIUse table here.

Also note that it is used primarily for multidimensional arrays (to avoid chaining map and flat, hence flatMap).