access a object value using a path like getDeepVal(obj, "foo.bar.baz")

getDeepVal.js

 /**
 * Access a deep value inside an object 
 * Works by passing a path like "foo.bar", also works with nested arrays like "foo[0][1].baz"
 * @author Victor B. https://gist.github.com/victornpb/4c7882c1b9d36292308e
 * Unit tests: http://jsfiddle.net/Victornpb/0u1qygrh/
 * @param {any} object Any object
 * @param {string} path Property path to access e.g.: "foo.bar[0].baz.1.a.b"
 * @param {any} [defaultValue=undefined] Optional value to return when property doesn't exist or is undefined
 * @return {any}
 */
function getDeepVal(object, path, defaultValue=undefined) {
   if (typeof object === 'undefined' || object === null) return defaultValue;
   const pathArray = path.split(/\.|\[["']?|["']?\]/);
   for (let i = 0, l = pathArray.length; i < l; i++) {
       if (pathArray[i] === '') continue;
       object = object[pathArray[i]];
       if (typeof object === 'undefined' || object === null) return defaultValue;
   }
   return (typeof object === 'undefined' || object === null) ? defaultValue : object;
}

setDeepVal.js

/**
 * Set a deep property on nested objects
 * @param  {object}   obj  A object
 * @param  {String}   path A path
 * @param  {Any}      val  Anything that can be set
 * @author Victor B. https://gist.github.com/victornpb/4c7882c1b9d36292308e
 */
function setDeepVal(obj, path, val) {
    var props = path.split('.');
    for (var i = 0, n = props.length - 1; i < n; ++i) {
        obj = obj[props[i]] = obj[props[i]] || {};
    }
    obj[props[i]] = val;
    return obj;
}