Array.map 1 element to multiple element

Question

I have [3, 16, 120]. when I do [3, 16, 120].map(mapper), I want to achieve, for example [4,5, 17,18, 121,122] i.e. each element map to n

Answer 1

Just for fun, an ES6 solution with a generator:

var arr = [3, 16, 120];

var [...result] = (function*() { for( i of arr){ yield ++i; yield ++i; }})();

console.log(result);