Javascript Data Types (String, Number, Boolean, Array, Object)

In this, we will go through all the data types of javascript in detail with examples.

What are data types?

• Data types in general define what specific kind of data we want to store in and get manipulated within the program.

So mainly the categories of DataTypes in javascript are:

1. Primitive data type
2. Composite data type (Non-Primitve)

So let’s explore these categories of data types one by one:

1.Primitive data type

These data types can hold only a single value. For example

• String
• Number
• Boolean

a. String data type

• To represent textual data we use String data type.
• Let’s say we want to create a sequence of characters So this is how we create them:

let name = “Siddhant”;

So you see above we used a variable let with variable name as name, our String in double quotes “ ” or you can use single quotation ‘ ‘ marks also and last but not least separating them with Assignment operator equal = symbol.

Quick Example:

let city = “New York”; // Using double quotes
let street_name = ‘E 5th Street’; // Using single quotes

Don’t be confused, In street_name the value is ‘E 5th Street’ String can have digits, Alphabets, and Symbols unless and until they are inside the quotation mark.

b. Number data type

• To represent a numerical value we use the Number data type.
• We can also define our numerical value as negative or positive, Integer, Float, hexadecimal, octal or exponential value.
• Always remember the first digit should always be an integer value in the number data type.
• And Most important do not use any quotation mark for the number data type.
• So this is how we create them:

let x = 55;

So you see we used again a variable let with variable name as x, our number value as 55 and separating them with Assignment operator equal = symbol.

Quick Example:

let ID = 2197; // positive integer
let score = 45.25; // Float
let blood_sugar = -20;  // negative integer
let Title_Color = 0x854712; // Hexadecimal
let problem = 2.06e+3; // exponential

c. Boolean data type

• In Boolean, we have two values either true or false.
• Mostly this type is used for conditional statements like if-else, else-if, switch, while, do...while, But it can also be defined as a value to a variable.
• Now have a look at how it is created:

let alive = true;

So you see we used a variable let with variable name as alive and alive status value as true and separating them with Assignment operator equal = symbol

Quick example:

let online_status = true;
let homework_submitted = false;

2. Composite data types

The composite data type is also known as the non-primitive data type. It can hold more collections of complex values. For example

• Array
• Object

a. Array

• In Array, we can store multiple values using a single variable.
• Every element in the array has a numerical index value, which shows the position of an element in the array.
• Arrays in javascript can have elements of different data types like String, boolean, number, object, function, and other arrays too.

Important note: The index of an array starts with 0, not from 1.

let myArray = [10,20,30,40,50];

So to create an array we first declare the variable, then inside the [ ] square brackets, there are elements separated by, comma.

Click here to know more about Array in javascript.

Let’s have a look at an example:

// Array With the same data type
let food = [“Pizza”, “Burger”, “Fries”, “cake”];
// Array with different data types.
let order = [25, “Burgers”, 50.99, true];

b. Object

• Object in javascript is a non-primitive data type that allows us to store multiple collections of data.
• For each data in an object, there is a property that is defined as a key-value pair, But these keys can always be a string and its value can be any data type like, number, string, boolean, array, function, and also other objects.

let myObj = { 
“height-Cm”: 175, 
“weight-lbs”: 275, 
“distance-km”: 75 
};

So you see we used curly brackets for our object inside that we defined property in double-quotes and assigned a value separated with : colon.

We can skip the double-quote unless we write our object as shown below:

let myObj = {
heightCM: 175, 
weightLBS: 275, 
distanceKM: 75
};

Quick example:

let online_shop = {
orderID: 57, 
itemName: “Shoes”, 
itemPrice: 399, 
payment: true, 
address: {
   block: 45, 
   street: “downtown street”, 
   city: “cape town”,
   pincode: 59595
},
ratings: [1,2,3,4,5]};

Bonus

There is also another category of data type that is:

3. Special data type

There are two special data types in javascript namely undefined and null.

a. Undefined data type

A variable that is declared but never assigned a value is undefined. Example :

let a;
console.log(a); // a is undefined

b. Null data type

• A variable that has only one value that is null itself.
• This clearly states that there is not value in the variable.
• And it is not the same as empty string or 0 or undefined.
• Null is specially passed to the variable.Example:

let a = null;
console.log(a); // a gives us null

Thank you for reading

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