Objects

Arrays hold ordered lists. Objects hold labeled properties — values stored under named keys.

What you'll learn

• Create objects with { key: value } literals
• Read, write, and delete properties
• Iterate over an object's keys or entries

Instructions

Write a function formatPerson(person) that takes an object with name and age properties and returns a string like "Ada is 36 years old.".

Example:

formatPerson({ name: "Ada", age: 36 }); // "Ada is 36 years old."

Key concepts

Object literals

Wrap key: value pairs in { ... }:

const person = { name: "Ada", age: 36 };

Keys are strings (you can leave quotes off if they're valid identifiers). Values can be any type — numbers, strings, arrays, even other objects.

Reading and writing properties

Two ways to access a property:

person.name;        // "Ada"   — dot notation
person["name"];    // "Ada"   — bracket notation

Dot notation is shorter; use brackets when the key is in a variable (person[keyName]).

Assign with =:

person.age = 37;
person.city = "London";   // adds a new property
delete person.city;        // removes it

Iterating

Object.keys(obj) gives you an array of keys; Object.entries(obj) gives [key, value] pairs:

for (const key of Object.keys(person)) {
  console.log(key, person[key]);
}

for (const [key, value] of Object.entries(person)) {
  console.log(`${key}: ${value}`);
}

Arrays vs. objects

Use an array for an ordered list of similar things ([1, 2, 3], ["a", "b"]). Use an object when values have distinct names ({ name, age, city }).

Hints

1. You can pull name and age straight out of the person argument with person.name and person.age.
2. Template literals (` ...${value}... `) make it easy to build the output string.
3. ` return ${person.name} is ${person.age} years old.; `