JavaScript Reference Type
JavaScript reference type.
- Object
- Array
- Functions.
Object
So, what is an object?
An object in JavaScript or other programming language is an object in
real life?
Think about person. A person has name, Age, address and so on, these are
the properties of the person we are in the same concept on the JavaScript.
When we dealing with multiple related variables, we can put these
variables inside of an object.
For example:
let name = ‘Emil’;
let age = 30;
Above two variables are highly related and representation of same person.
Instead of declaring two variables, we can declare a person as object.
Instead of referring these two variables, we can just reference person
object.
It makes our code cleaner
so how to declared person’s object
let name = ‘Emil;
let age = 30;
Instead of above code we can declare as object {} curly brackets called object literal
let
person = {
name: ‘Emil’,
age: 30;
};
Comma (,) to add another key value
Properties of the object
Two key values Name and Age
Now log person in console Console.log(person);
Answer =
{name: “Emil”, age.: 30}
age: 30
name: “Emil”
There are two ways to work with these properties.
Let’s say we want to change the name of this person.
1.First way .dot notation
Person.name
=’John’;
Console.log (person)
We can also use dot notation to read the property
Console.log (person.name);
In console you get John.
Another way to access the property we can use []
Bracket notation
2.Second Way [] Bracket notation
person[‘name’] =’Mary’;
console.log (person.name);
Now save the change you can see Mary
on the console.
Which approach is better? Dot notation or Bracket notation
Bracket notation have more features. Bracket notations have it’s one uses .
For example: sometimes you do not know the name or target property
until the runtime.
In your user interface, the user might be selecting the name of the
target property, in that case the term of writing code, we do not know what
property we’re going to access. That is going to be selected at one point of
time by user.
So, we might have another variable.
Somewhere else like selection.
Bracket notation []
let selection
= ‘name’;
Person [‘selection’]
= ’Mary’;
Console.log(person.name);
Determining the target property, the user is selecting.
We can access the property using the bracket notation in dynamic way.
So, we pass the selections here and we get the same result.