javascript – How can I refactor nested _.each so that it is more readable?

Hello dear developers.
I have created code to prepare the internal cache (4-dimensional array) with the use of underscore.js (nesting _.each 3 times)

Can you help me improve its readability or indicate the direction to follow to improve my code by using underscore.js / javascript in a more elegant way?

_.each (_playlist, function (episode) {
if (episode && episode.match && episode.match.abc_videos && episode.match.abc_videos.periods)
_.each (episode.match.abc_videos.periods, function (period, pid) {
periodId = pid;

if ( {
// define base indexes for abc period types //
_.each (, function (abc, index) {
var abcType = abc.abc_type;

link to gist: