So I have an array of objects userEvents that I want to use the event array inside of the object. The event array is storing objects as well, in which I am trying to access the start property and change it. I was thinking about nesting map functions, but I have had no success. I attached the console log of array of userEvents 
const { events } = this.props.events;
const userEvents = events
Giving you just want
access
startproperty
userEvents.forEach(userEvent => userEvent.events
.forEach(event => { console.log(event.start) })
)
You have an array that basically simplifies to this:
let userEvents = [
{events: [{start: 1},{start: 2}]},
{events: [{start: 3},{start: 4}]}
]
You should be able to loop through userEvents, then inside that, look at each element's events array and loop through that:
let userEvents = [
{events: [{start: 1},{start: 2}]},
{events: [{start: 3},{start: 4}]}
]
userEvents.forEach(e => {
e.events.forEach(event =>{
console.log(event.start)
})
})This will get you access to the elements you want. If you are trying to extract these or turn them into a different data format, of course tools like map(), filter(), and reduces() will be helpful.
For example, getting all your starts as an array:
let userEvents = [
{events: [{start: 1},{start: 2}]},
{events: [{start: 3},{start: 4}]}
]
let starts = userEvents.reduce((a, e) => {
return [...a, ...e.events.map(event => event.start)]
}, [])
console.log(starts)
const { events: userEvents } = this.props.events