So I have this nested array:
a1 = ['one', 'two', ['three', 'four']];
My goal is to extract the elements 'three' and 'four' from the child array and combine them with the parent array as a single string like so:
a2 = ['one', 'two', 'three, four'];
I'm wondering if there's an ES6 solution for this. And also, please note that there should be a space between 'three' and 'four' in the final array.