javascript indexOf object value in array

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

console.log(index);

// Get index of object with specific value in array
const needle = 3; // needle
const haystack = [{ id: 1 }, { id: 2 }, { id: 3 }]; // haystack
const index = haystack.findIndex(item => item.id === needle);

// Get index of object with specific value in array
const needle = 3;
const haystack = [{ id: 1 }, { id: 2 }, { id: 3 }];
const index = haystack.findIndex(item => item.id === needle);

        
            
        
     let ranks = [1, 5, 7, 8, 10, 7];
let index = ranks.findIndex(rank => rank === 7);
console.log(index);