问如果javascript中的值相同，如何再次使用math.random来获取不同的值

EN

function rands() {
  return Math.floor(Math.random() * 20) + 1;
}

var rand1 = rands();
var rand2 = rands();
var rand3 = rands();
var rand4 = rands();
var rand = [];

function myFunction() {
  document.getElementById("random1").value = rand1;
  document.getElementById("random2").value = rand2;
  document.getElementById("random3").value = rand3;
  document.getElementById("random4").value = rand4;

  if(rand1 == rand2 || rand1==rand3 || rand1==rand4 || rand2 == rand3 || rand2 == rand4 || rand3==rand4){
  console.log("Duplicate");

    }
}

myFunction()