JSFiddle - React, Tailwind, and code Playground

HTML

<div id="result"></div>

JavaScript

var parents = 
    [{
        name: 'hello',
        items: [ 'a', 'b' ]
    },
    {
        name: 'world',
        items: [ 'c', 'd' ]
    }];

var allitems = _.flatten(_.pluck(parents, 'items'));
document.getElementById('result').innerHTML = allitems;