Objects in Javascript

hello

In this article, we will be discussing javascript objects.

We will see :

What are javascript objects
Different ways of creating them
Different ways of accessing them

What are javascript objects?

Javascript objects are similar to real-world objects. Take an example of a car. A car is an object with different properties like color, model, etc.

Objects are used to store key-value store of data and multiple entities. Unlike primitive data types where value contains a single thing(string or number), objects can store multiple data types and even functions.

Ways to create objects

Objects literal

  const user = {    
  name: "Aaku",  
  age: 23        
}

In the user object, there are two properties :

name which has value "Aaku"
age which has value 23
new keyword

let user = new Object()
user.name="Aaku"
user.age=23

Accessing the properties of the object

dot notation

let user = {
    name: "Aaku"
}

console.log(user.name)

brackets notation

let user = {
    name: "Aaku"
}

console.log(user["name"])

Bonus 💥

"in" operator

In javascript, there will be no error if the property does not exist. It will simply return undefined. Example:

let user = {};

console.log( user.noSuchProperty === undefined ); // true means "no such property"

for..in loop It is used to iterate over all the keys of the object.

for (let key in user) {
  // keys
  alert( key );  // name, age
  // values for the keys
  alert( user[key] ); // Aaku, 23
}

Checking for emptiness

function isEmpty(obj) which returns true if the object has no properties, false otherwise.

function isEmpty(obj) {
  for (let key in obj) {
    // if the loop has started, there is a property
    return false;
  }
  return true;
}

References

MDN Docs

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