random.ts

function randomSelection<T>(numToSelect: number, list: T[]): T[] {
  return take(numToSelect, randomizeList(range(0, list.length)))
    .map((i) => list[i]);
}
function randomizeList<T>(xs: T[], randomized: T[] = []): T[] {
  if (xs.length) {    
    const {arr, val} = slice(Math.floor(Math.random() * xs.length), xs);
    return randomizeList(arr, randomized.concat([val]));
  }
  return randomized;
}

function slice<T>(pos: number, xs: T[]): {arr: T[], val: T} {
  return ({ val: xs[pos], arr: xs.slice(0, pos).concat(xs.slice(pos+1))});
}
function take<T>(num: number, xs: T[]): T[] {
  return num === 1 ? head(xs) : [head(xs)].concat(take(num - 1, tail(xs)))
}
function head<T>(xs: T[]): T {
  return xs[0];
}
function tail<T>(xs: T[]): T[] {
  return xs.slice(1);
}
function range(start: number, end: number): number[] {
  return Array.from(new Array(end - start), (_, i) => i + start);
}

console.log(randomSelection(3, [1,2,3,4,5,6,7,8,9,10]))
console.log(randomSelection(2, ['john', 'jazz', 'stan', 'ethan']));