flattenObject.js

function flatten(object, path, result) {
  if (!result) {
    result = {};
  }
  for (let prop in object) {
    if (typeof object[prop] !== 'object') {
      result[path ? path + prop : prop] = object[prop];
    } else {
      flatten(object[prop], path ? path + prop + '.' : prop + '.', result);
    }
  }
  return result;
}

describe('flatten', function() {

  it('basic case', function() {
    flatten({ a: 1, d: 2}).should.deep.equal({ a: 1, d: 2});
  });

  it('complex case', function() {
    const res = flatten({ a: { b: { c: 1 } }, d: 2});
    res.should.deep.equal({ 'a.b.c': 1, d: 2});
  });

  it('complex case 2', function() {
    const res = flatten({ a: { b: { c: 1 } }, d: { e: 2 }, f: 34});
    res.should.deep.equal({ 'a.b.c': 1, 'd.e': 2, f: 34});
  });

});