recursion examples

deepSum.js

// takes in any structure
// returns the sum of all numbers in all leaf nodes recursively
function deepSum (json) {
  if (Array.isArray(json)) {
    return json.reduce((sum, item) => sum + deepSum(item), 0)
  } else if (typeof(json) === 'object') {
    return Object.keys(json)
      .reduce((sum, key) => sum + deepSum(json[key]), 0)
  } else {
    try {
      return Number(json) || 0
    } catch (e) {
      return 0
    }
  }
}

// tail recursive version
// refactored for Object.values
function deepSum (json, sum = 0) {
  if (typeof(json) === 'object') {
    let items = (Array.isArray(json) ? json : Object.values(json))
    return items.reduce((_sum, item) => deepSum(item, _sum), sum)
  } else {
    try {
      return sum + (Number(json) || 0)
    } catch (e) {
      return sum
    }
  }
}