const lst = [[0, 0], [5, 4], [3, 1]];
const center = [1, 2];
const k = 2;

const findNearestPoints = ({lst, center, k}) => {
  // I assume the data are valid; no error checks
  const calcHypo = x => Math.sqrt((x[0] - center[0])**2
                                + (x[1] - center[1])**2);
  const sortPoints = (a,b) => calcHypo(a) - calcHypo(b);
  return lst
   .sort(sortPoints)
   .slice(0,k);
};

console.log(findNearestPoints({lst, center, k}));