Data Types are important concepts in any language. They define the type of data a variable can hold.
In JavaScript, we have various data types like:
The
typeof()
function can be used to see the data type of the variable.
Number
This data type can hold integers from -Infinity to +Infinity including floating-point numbers.
var a = 2;
console.log(typeof(a)); // "number"
var b = 3.56;
console.log(typeof(b)); // "number"
String
A String is a sequence of characters. String are denoted using " "
or ' '
var name = "Developer";
console.log(typeof(name)); // string
var letter = "A";
console.log(typeof(letter)); // string
Boolean
A boolean is a true
or false
value.
var isRaining = true;
console.log(typeof(raining)); // boolean
var isLoggedIn = false;
console.log(typeof(isLoggedIn)); // boolean
Arrays
Arrays are a collection of similar data types. They are denoted using square brackets [ ]
var numbers = [1, 2, 3, 4, 5]; // array of numbers
var colors = ["red", "green", "blue"]; // array of strings
But, in JavaScript, an array can hold various data types too.
var numbersAndColors = [1, "blue", 2, "red", 3];
You can access the value of the array by its index. Every array has an index that starts with 0.
console.log(colors[0]); //red
console.log(colors[1]); //green
console.log(numbers[0]); // 1
console.log(numbers[1]); // 2
Object
In JavaScript, an object is a collection of key: value pairs.
They are denoted using the {}
brackets
var obj = {
name: "Shubham",
age: 20,
role: "Frontend Developer",
isStudent: true,
hobbies:['coding","reading","eating"]
};
Each object's key: value pair must be separated by a comma.
The data of an object can be accessed by the following syntax.
Syntax:
ObjectName.keyName
= if the key is a String.ObjectName[keyName]
= if the key is a Number
var obj = {
name: "Shubham",
age: 20,
role: "Frontend Developer",
100: "Hundred",
};
console.log(obj.name); // "Shubham"
console.log(obj.age); // 20
console.log(obj[100]); // "Hundred"
null
A null data type means that value doesn't exist in memory.
undefined
An undefined type means that value exists but is not yet defined.
var a;
console.log(a); // undefined
These are the basics data types present in JavaScript.
Next, we will learn about JavaScript Operators.