JavaScript Object Methods with Examples

JavaScript object methods are simple ways to handle data inside objects. An object can hold many values, and methods give direct access to those values.

Understand the Methods in JavaScript Object

A method is a function that lives inside an object. It acts on the data of that object and can return useful results.

The syntax has a function placed inside an object with a name. That function then becomes a method.

Here is an example:

let user = {
  name: "John",
  greet: function() {
    return "Hello " + this.name;
  }
};

The method greet uses this.name to read the value of the key inside the same object.

JavaScript connects the keyword this to the current object. The code inside runs with the object values when you call the method.

The Object.keys() takes all keys from an object and gives them as an array.
Object.values() does the same but returns the values.

let car = { brand: "Ford", year: 2021 };
console.log(Object.keys(car));   // ["brand","year"]
console.log(Object.values(car)); // ["Ford",2021]

These two methods allow you to see what the object holds without manual loops.

Object.assign() and Cloning Objects

You can use Object.assign() to copy data from one object to another. It can help when you need a clone of an object.

let base = { a: 1, b: 2 };
let copy = Object.assign({}, base);
console.log(copy); // { a:1, b:2 }

The method joins values from the source into a target, and hence it helps in clone tasks.

Object.entries() for Iteration

This method returns key and value pairs inside arrays. You can then use loops like for...of to run through them.

let data = { x: 10, y: 20 };
for (let [key, value] of Object.entries(data)) {
  console.log(key + ":" + value);
}

This way you can deal with both parts of the object in one pass.

Object.freeze() and Object.seal()

The Object.freeze() blocks changes to the object. Object.seal() allows updates of old values but does not allow new keys. Both methods help to control object safety in code.

For example:

// Example with Object.freeze()
const user1 = { name: "Ali", age: 25 };
Object.freeze(user1);

user1.age = 30;      // No change
user1.city = "Riyadh"; // No new property
console.log(user1);  // { name: "Ali", age: 25 }

// Example with Object.seal()
const user2 = { name: "Sara", age: 20 };
Object.seal(user2);

user2.age = 22;      // Value updated
user2.city = "Jeddah"; // No new property
console.log(user2);  // { name: "Sara", age: 22 }

• freeze stops both updates and new keys.
• seal allows updates but blocks new keys.

Create Custom Object Methods

You can also make your own method inside an object. A custom method can do any action you need with that object.

let bank = {
  balance: 1000,
  deposit: function(amount) {
    this.balance = this.balance + amount;
  }
};
bank.deposit(500);
console.log(bank.balance); // 1500

The method acts like a rule inside the object and keeps track of its data.

Examples

Count Keys in Object:

let fruit = { apple: 5, orange: 10, banana: 7 };
let count = Object.keys(fruit).length;
console.log("Total keys: " + count);

This example counts all keys inside the object with Object.keys().length. It shows how you can find the number of keys with one step instead of loops.

Merge Objects with Object.assign():

let a = { id: 1, name: "Sam" };
let b = { age: 25, city: "Paris" };
let result = Object.assign({}, a, b);
console.log(result);

Here is two objects joined into one with Object.assign(). This method is useful when you need to combine user data and extra data into a single structure.

Freeze Object to Protect Data:

let config = { host: "localhost", port: 3000 };
Object.freeze(config);
config.port = 4000;
console.log(config.port);

In this case the port stays at 3000 even after you try to set a new value. The Object.freeze() method protects the object so no one can make changes.

Loop with Object.entries():

let scores = { math: 90, english: 85, science: 92 };
for (let [subject, mark] of Object.entries(scores)) {
  console.log(subject + " score is " + mark);
}

This example shows how to loop through subjects and marks with Object.entries(). The loop prints each subject name with its mark in a simple, readable way.

Wrapping Up

In this article, you learned how methods in JavaScript objects work and how they can control data in many ways. Here is a quick recap:

• You saw how methods live inside objects as functions.
• You learned how to use keys and values.
• You saw how to clone and freeze. Also, understood how to seal objects.
• You built custom methods and used real examples.

FAQs

const obj = {name: 'John', age: 30};
const keys = Object.keys(obj);
console.log(keys); // ['name', 'age']

const obj1 = {a: 1};
const obj2 = Object.assign({}, obj1); // shallow copy
// Object.assign copies properties into a new object

const obj = {x: 10, y: 20};
for (const [key, value] of Object.entries(obj)) {
  console.log(key, value);
}
// Output: x 10
//         y 20

const obj = {name: 'Alice'};
Object.freeze(obj); // Prevents changes entirely
Object.seal(obj);   // Allows changes to values but not keys

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