ReactJS, How to get the oldest and newest date from array using moment.js

Sort the dates array and grab the last one.

DatosFechas = ["2020-04-29", "2020-04-19", "2020-04-07", "2020-04-30", "2020-04-30", "2018-01-22"]
const sortedDates = DatosFechas.sort((a, b) => moment(a) - moment(b));
console.log('NEWEST Date',sortedDates[sortedDates.length-1])
console.log('OLDEST Date',sortedDates[0])

Note: You don't really need moment for your case. You can use js inbuilt Date feature. See here

You are doing great, you have done right. Just problem is that you have to formant your return moment object instead of returning it as an object.

Use it-

function ObtenerMaxMinRangoFechas(DatosFechas) {
    const moments = DatosFechas.map(x => moment(x));
    const maxDate = moment.max(moments);
    return maxDate.format('YYYY-MM-DD');
}

In what format do you want to return the first and last date? Here is an example with an array of the first and last string:

let dates = ["2020-04-29", "2020-04-19", "2020-04-07", "2020-04-30", "2020-04-30", "2018-01-22"]

const getFirstAndLastDate = (dates) => {
  dates = dates.sort()
  return [dates[0], dates[dates.length - 1]]
}

console.log(getFirstAndLastDate(dates))

Moment.max seems to be returning an moment object rather than a string in the format you want. to get the string format, you'll need to call format and pass the format you want, like this

moment.format('YYYY-MM-DD')  

let's put this together,

function ObtenerMaxMinRangoFechas(DatosFechas) {
    let moments = DatosFechas.map(x => moment(x)),
    maxDate = moment.max(moments).format('YYYY-MM-DD');
    return maxDate
}