getIn-example.js

// Data
var object = { 'a': [{ 'b': { 'c': 3 } }] };
var object2 = {a: { b: { c: 3 } } };
// Function helper to get the type of Param
const getTypeOfParam = (value) => Object.prototype.toString.call(value).replace(/^\[object |\]$/g, '').toLowerCase();

const getIn = (obj, path, defaultValue) => {
  // validate params
  if (getTypeOfParam(obj) !== 'object') throw new TypeError('the first param should be a object');
  if (getTypeOfParam(path) !== 'string') throw new TypeError('the second param should be a object');
  let value = {};
  path.split('.').forEach((p, i) => {
    // check if the value of path exists, if not return the defaultValue
    value = i === 0 ? obj[`${p}`] : ( value[`${p}`] ? value[`${p}`] : defaultValue );
  });
  console.log('value', value);
  return value;
}
getIn(object, 'a.b.c', 'default');
// => 'default'
getIn(object, 'a.0.b.c', 'default');
// => 3
getIn(object2, 'a.b.c', 5);
// => 3
getIn(object2, 'a.b.d', 5) ;
// => 5