Practice Questions — Objects and JSON

const obj = { name: "Aarav", age: 15 };
console.log(obj.name);
console.log(obj.age);

const student = { name: "Priya", grade: "10th" };
const key = "grade";
console.log(student[key]);

const obj = { a: 1, b: 2, c: 3 };
console.log(Object.keys(obj));

const obj = { x: 10, y: 20 };
obj.z = 30;
console.log(obj);

const scores = { maths: 95, science: 88 };
console.log(Object.values(scores));

const { name, age } = { name: "Rohan", age: 16, grade: "11th" };
console.log(name);
console.log(age);

const person = {
  name: "Kavya",
  greet() {
    return "Hi, " + this.name;
  }
};

console.log(person.greet());

const a = { x: 1 };
const b = { ...a, y: 2 };
console.log(b);
console.log(a);

const obj = { a: 1, b: 2, c: 3 };
const entries = Object.entries(obj);
console.log(entries);

const student = {
  name: "Diya",
  address: {
    city: "Chennai",
    state: "Tamil Nadu"
  }
};

console.log(student.address.city);
console.log(student.phone?.number);

const obj = { name: "Vikram" };
const json = JSON.stringify(obj);
console.log(json);
console.log(typeof json);

const defaults = { color: "red", size: 10 };
const custom = { size: 20, weight: 5 };
const merged = { ...defaults, ...custom };
console.log(merged);

const a = { data: [1, 2, 3] };
const b = { ...a };
b.data.push(4);
console.log(a.data);

const a = { name: "Meera" };
const b = { name: "Meera" };
const c = a;

console.log(a === b);
console.log(a === c);

const { name: studentName, age: studentAge = 18 } = { name: "Arjun" };
console.log(studentName);
console.log(studentAge);

const person = {
  name: "Aarav",
  greet: () => {
    return "Hi, " + this.name;
  }
};

console.log(person.greet());

const student = {
  name: "Priya",
  marks: { maths: 92, science: 88 }
};

const { marks: { maths, science } } = student;
console.log(maths);
console.log(science);

const obj = { a: 1, b: 2, c: 3 };
delete obj.b;
console.log(obj);

const json = '{"name":"Diya","age":14}';
const obj = JSON.parse(json);
console.log(obj.name);
console.log(typeof obj);

const person = { name: "Kabir", age: 17 };
console.log("name" in person);
console.log("email" in person);

const obj = { x: 10, y: 20, z: 30 };
const sum = Object.values(obj).reduce((a, b) => a + b, 0);
console.log(sum);

const obj = { a: 1, b: 2, c: 3 };
const filtered = Object.entries(obj)
  .filter(([key, val]) => val > 1)
  .map(([key, val]) => key);
console.log(filtered);

const student = { name: "Ananya", grade: "10th" };
const { name, ...rest } = student;
console.log(name);
console.log(rest);

const key = "color";
const value = "purple";
const obj = { [key]: value };
console.log(obj);

const students = [
  { name: "Aarav", marks: 72 },
  { name: "Priya", marks: 91 },
  { name: "Rohan", marks: 85 },
  { name: "Diya", marks: 68 }
];

const names = students
  .filter(s => s.marks >= 70)
  .sort((a, b) => b.marks - a.marks)
  .map(s => s.name);

console.log(names);

const obj = {
  count: 0,
  increment() {
    this.count++;
    return this;
  },
  getCount() {
    return this.count;
  }
};

console.log(obj.increment().increment().increment().getCount());

const data = '{"students":[{"name":"Meera","score":88},{"name":"Kabir","score":92}]}';
const parsed = JSON.parse(data);
console.log(parsed.students[1].name);
console.log(parsed.students.length);

const obj = { a: 1, b: 2 };
const copy = Object.assign({}, obj, { c: 3 });
console.log(copy);
console.log(obj);

const obj = { name: "Ishaan", age: 13 };
console.log(obj.hasOwnProperty("name"));
console.log(obj.hasOwnProperty("email"));

const people = [
  { name: "Aarav", city: "Delhi" },
  { name: "Priya", city: "Mumbai" },
  { name: "Rohan", city: "Delhi" },
  { name: "Diya", city: "Mumbai" }
];

const grouped = people.reduce((acc, person) => {
  const city = person.city;
  acc[city] = acc[city] || [];
  acc[city].push(person.name);
  return acc;
}, {});

console.log(grouped);

const obj = { a: 1, b: 2, c: 3 };
for (const [key, val] of Object.entries(obj)) {
  console.log(key + " = " + val);
}