JavaScript Program to Loop Through an Object

Example 1: Loop Through Object Using for...in

// program to loop through an object using for...in loop

const student = { 
    name: 'John',
    age: 20,
    hobbies: ['reading', 'games', 'coding'],
};

// using for...in
for (let key in student) { 
    let value;

    // get the value
    value = student[key];

    console.log(key + " - " +  value); 
} 

Output

name - John
age - 20
hobbies - ["reading", "games", "coding"]

In the above example, the for...in loop is used to loop through the student object.

The value of each key is accessed by using student[key].

Note: The for...in loop will also count inherited properties.

For example,

const student = { 
    name: 'John',
    age: 20,
    hobbies: ['reading', 'games', 'coding'],
};

const person = {
    gender: 'male'
}

// inheriting property
student.__proto__ = person;

for (let key in student) { 
    let value;

    // get the value
    value = student[key];

    console.log(key + " - " +  value);
} 

Output

name - John
age - 20
hobbies - ["reading", "games", "coding"]
gender - male

If you want, you can only loop through the object's own property by using the hasOwnProperty() method.

if (student.hasOwnProperty(key)) {
    ++count:
}

Example 2: Loop Through Object Using Object.entries and for...of

// program to loop through an object using for...in loop

const student = { 
    name: 'John',
    age: 20,
    hobbies: ['reading', 'games', 'coding'],
};

// using Object.entries
// using for...of loop
for (let [key, value] of Object.entries(student)) {
    console.log(key + " - " +  value);
}

Output

name - John
age - 20
hobbies - ["reading", "games", "coding"]

In the above program, the object is looped using the Object.entries() method and the for...of loop.

The Object.entries() method returns an array of a given object's key/value pairs. The for...of loop is used to loop through an array.