function getDayName(dateString) {
    return  ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"][new Date(dateString).getDay()];
}``

This is my solution , guess what , it is the easiest solution for this problem.

function getDayName(dateString) { let dayName; let days = { Sun: "Sunday", Mon: "Monday", Tue: "Tuesday", Wed: "Wednesday", Thu: "Thursday", Fri: "Friday", Sat: "Saturday"

}
let day  = new Date(dateString)
let arr = day.toString().split(' ')
let dayshort = arr[0]
dayName = days[dayshort]


return dayName;

}

Here is a simple solution without using any map or map object.

let dayName = new Date(dateString).toLocaleDateString(undefined, {weekday: "long"});
return dayName;

function getDayName(dateString) { let dayName; // Write your code here let dayweeks = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"] dayName = new Date(dateString).getDay() return dayweeks[dayName]; }