Coding exercise - prime tables

Coding challenge for interview with Find My Past. This programme takes a numeric input (N) from a user and outputs a multiplication table of (N) prime numbers.

This programme runs in the browser. Please open this page to see it in action.

This project contains four functions that all perform specific tasks.

function isPrime() tests whether a given number input is prime.
function primesArray() takes a number input (n) from the user and generates an array of prime numbers of length (n). I believe that the big O notation of this part of the programme is O(n).
function multiplyPrimes() calls primesArray() and returns a nested array of multiples of the zero indexed array. I believe this is the least efficient part of the programme with a Big O notation of O(n2).
function onSubmit() takes the input (n) from the user and checks to see if it is greater than 1. Then it calls multiplyPrimes() and outputs the return value onto the page as a multiplication table. I believe that the forEach() function within this function has a Big O Notation of O(n).

Example output (user input 3)

|2|3|5
2|4|6|10
3|6|9|15
5|10|15|25

Testing 🧪

I wrote tests to cover the first three functions listed above. The tests output as expected:

I wasn't able to extract the logic to perform seperate tests on each step in the onSubmit() function. See below for what I would do if I had more time.

Screenshots 👀

Mobile view:

Desktop view:

User input:

What I'm pleased with

I'm pleased that the programme runs with large numbers without hanging the browser.
I like the use of template strings to display the multiplication table.

What I would like to do next

Separate out the logic contained within the onSubmit() function into different functions. This would enable better unit testing (see above).
Try to find a more efficient way of producing the multiplication table without nested arrays
Try to find a better way of displaying larger outputs onto the page. Right now they require the user to scroll/stretch the layout.
I could also try to implement a version of the Sieve of Eratosthenes to check the primes.

Moggach / primes_test