Answers for "given a number n for each integer i in the range from 1 to n javascript"

javascript generate a random integer number in a range of numbers

const min = 1;
const max = 4;
const intNumber = Math.floor(Math.random() * (max - min)) + min;
console.log(intNumber); //> 1, 2, 3

sum all numbers in a range javascript

ar sum = 0;
  for (var i = Math.min(...arr); i <= Math.max(...arr); i++) {
    sum += i;
  }