if value in list javascript and return index

a = [
  {prop1:"abc",prop2:"qwe"},
  {prop1:"bnmb",prop2:"yutu"},
  {prop1:"zxvz",prop2:"qwrq"}];
    
index = a.findIndex(x => x.prop2 ==="yutu");

console.log(index);var scores = [10, 20, 30, 10, 40, 20];
console.log(scores.indexOf(30)); // 2
console.log(scores.indexOf(50)); // -1