find_demo.js

var empEligibilityDetails = [
    {
      "name": "Vishal",
      "age": 30,
      "isManager": false,
      "city": "Mumbai"
    },
    {
      "name": "Kunal",
      "age": 31,
      "isManager": false,
      "city": "Pune"
    },
    {
      "name": "Ajay",
      "age": 32,
      "isManager": true,
      "city": "Thane"
    },
    {
      "name": "Rahul",
      "age": 36,
      "isManager": true,
      "city": "Mumbai"
    }
  ];

var empData = empEligibilityDetails.find(value => value.age > 31);
console.log(empData); 

//If you want to skip 1st record, you can play with index passed in argument
var empNewData = empEligibilityDetails.find((value, i) => {
    if (value.age > 28 && i !== 0) return true;
});
console.log(empNewData); 

empEligibilityDetails.find(value => value.age > 31).isManager = false;
console.log(empEligibilityDetails);