How to generate Random numbers, then exclude array of numbers

i would like to generate random numbers from 1-50, then exclude an array like; 4,7,10,20,35 etc

i tried this;

let mainNum = 50
let exclNum = [4, 7, 10, 20, 35];
if (!exclNum.includes(mainNum)) {
  console.log(Math.floor(Math.random() * mainNum) + 1)
}

but it still generates numbers that's still in the array, please is there anything i am missing?

Thanks for your response in advance