recursive.js

function recursive (obj, tab = '') {
  let keys = []
  try {
    keys = Object.keys(obj)
  } catch (err) {
    throw new Error(err)
  }
  keys.forEach((key) => {
    if (obj[key] !== null
        && typeof obj[key] === 'object') {
      console.log('%s: =>', key)
      recursive(obj[key], '  ')
    } else {
      console.log('%s%s: %s', tab, key, obj[key])
    }
  })
}

recursive({
  a: 1,
  b: 'bbb',
  c: {
    ac: 1,
    bc: 'bcbcbc'
  },
  d: [1, 2]
})