function addUpTo(n) {

    let total = 0;
    for (let i = 1; i<= n ; i++){
        total +=1
    }
    return total;
}
var t1 = performance.now()
addUpTo(1000000000)
var t2 = performance.now()

console.log(`Time Elapse: ${(t2 - t1) / 1000} second. `)

function addUpTo(n) {
    return n * (n+1) / 2;
}
var t1 = performance.now()
addUpTo(1000000000)
var t2 = performance.now()

console.log(`Time Elapse: ${(t2 - t1) / 1000} second. `)