Creating a for loop in javascript

Question

I am trying to make this for loop work, my assignment is;

We want to write a function summation that will find the sum of all the values from 1 to (and including) n. The value n is passed into our function.

Similar to the for loop above, you can initialize some value i to start at 1. The value should reach n but never exceed it.

My code is;

function summation(n) {
 let sum = 0;
 for (let i = 1; i <= n; i++) {
 sum = sum + n;
 }
 return sum + i;
}
module.exports = summation;

---

Getting these errors;

summation
 1) should sum up to 2
 2) should sum up to 3
 3) should sum up to 4
 0 passing (5ms)
 3 failing
 1) summation
 should sum up to 2:
 ReferenceError: i is not defined
 at summation (summation.js:8:14)
 at Context.<anonymous> (test/test.js:6:22)
 at processImmediate (internal/timers.js:461:21)
 2) summation
 should sum up to 3:
 ReferenceError: i is not defined
 at summation (summation.js:8:14)
 at Context.<anonymous> (test/test.js:9:22)
 at processImmediate (internal/timers.js:461:21)
 3) summation
 should sum up to 4:
 ReferenceError: i is not defined
 at summation (summation.js:8:14)
 at Context.<anonymous> (test/test.js:12:22)
 at processImmediate (internal/timers.js:461:21)

• Barmar: return sum + i should be just return sum

Answer 1

You should be adding i to sum inside the loop, not after the loop is done. You can't access i after the loop, because let i declares the variable to be local to the loop.

function summation(n) {
 let sum = 0;
 for (let i = 1; i <= n; i++) {
 sum = sum + i;
 }
 return sum;
}
console.log(summation(2));
console.log(summation(3));
console.log(summation(4));