How to traverse a tree recursively?

Question

JavaScript

How to recursively get width value from all nesting levels?
jsbin.com/gecabacu/1/edit?js

Answer 1

const getWidths = data =>
  [].concat(data || []).reduce((acc, n) => {
    if (n.hasOwnProperty('width')) {
      acc.push(n.width);
    }
    acc.push(...getWidths(n.columns));
    return acc;
  }, []);

https://jsfiddle.net/jf0hsm6c/

Answer 2

for in + recursion. Or is it as difficult as using the "code" button to properly format the question?