JavaScript Data Types

JavaScript data types are used to specify what kind of data can be stored and manipulated in a program. JavaScript data types tell the compiler whether the data value is numeric, alphabetic, date, etc. so that it can perform the appropriate operation.
Primitive data types can hold only one value at a time and non-primitive data types can hold collections of values and more complex entities.

JavaScript data types are divided into two main categories:

Primitive Data Types:

Non-primitive Data Types:

Primitive Data Types:

The String Data Type:

The data type string is used to represent textual data i.e. sequences of characters and the strings are created using single or double-quotes.

Example:

var a = 'Hello'; // using single quotes

var b = "Learn JavaScript"; // using double quotes

You can include quotes inside the string as long as they don’t match the enclosing quotes.

Example:

var a = "Let's learn JavaScript";

var b = 'He said "Hello" and left.';

var c ="He said 'Hello' and left.";

You will learn more about the strings in our JavaScript strings topic.

The Number Data Type:

The data type number is used to represent positive or negative numbers with or without decimal place, or numbers are written using exponential notation e.g. 1.5e-4.

Example:

var a = 24.00;

var b = 24;

var c = 2.47;

document.getElementById("trial").innerHTML = a + " " + b + " " + c;

The extra-large or extra small numbers in JavaScript can be written with the exponential notation.

Example:

var a = 456e5;

var b = 456e-5;

document.getElementById("trial").innerHTML = a + " " + b;

You will learn more about the strings in our JavaScript numbers topic.

The Boolean Data Type:

The Boolean data type holds only two values i.e true or false. It is used to store values like yes (true) or no (false), on (true) or off (false), etc.

Example:

var a = 6;

var b = 7;

var c = 6;

document.getElementById("trial").innerHTML = (a == b) + " " + (a == c);

The Undefined Data Type:

The undefined data type can only have one value i.e undefined. If a variable is declared but the value is not assigned to it then it has the value undefined.

Example:

var a; // Value is undefined, type is undefined

document.getElementById("trial").innerHTML =

a + " " + typeof a;

The Null Data Type:

In JavaScript, a null value means that there is no value, it is not equivalent to an empty string (“”) or 0, it is simply nothing. It has only one value i.e the null value.
A variable can be explicitly emptied of its current contents by assigning it to the null value. In JavaScript, the data type of null is an object.

Emptying an object by setting it to null:

Example:

var person = {firstName:"David", lastName:"Miller", age:30, eyeColor:"brown"};

person = null; //Value is null, but type is still an object

document.getElementById("trial").innerHTML = typeof person;

Emptying an object by setting it to undefined:

Example:

var person = {firstName:"David", lastName:"Miller", age:30, eyeColor:"brown"};

person = undefined; // Both value and type is undefined

document.getElementById("trial").innerHTML = person;

Non-primitive Data Type:

The Object Data Type:

The object is a non-primitive data type that allows you to store collections of data. An object contains properties and defined as a key-value pair. A property key (name) is always a string, but the value can be any data types, like strings, numbers, booleans, or complex data types like arrays, function and other objects.

Example:

var person = {

firstName : "David",

lastName : "Miller",

technology: "JavaScript"

};

document.getElementById("trial").innerHTML =

person.firstName + " is learing " + person.technology + ".";

The Array Data Type:

An array is object type is used for storing multiple values in a single variable. Each value in an array has a fixed position, known as its index, and it may contain data of any data type-numbers, strings, booleans, functions, objects, and even other arrays. The array index starts from 0 so the first array element is arr[0], not arr[1].
The easiest way to create an array is by specifying the array elements as a comma-separated list enclosed by square brackets.

Example:

var technologies = ["HTML","CSS","JavaScript", "jQuery"];

document.getElementById("trial").innerHTML = technologies[2];

The typeof Operator:

The typeof operator is used to find out what type of data a variable contains. It is used with or without parentheses (typeof(x) or typeof x).

Example:

document.getElementById("trial").innerHTML =

typeof "" + " " + // Returns "string"

typeof "David" + " " + // Returns "string"

typeof "David Miller" + " " + // Returns "string"

typeof 0 + " " + // Returns "number"

typeof 24 + " " + // Returns "number"

typeof 2.47 + " " + // Returns "number"

typeof (2) + " " + // Returns "number"

typeof (2 + 3); // Returns "number

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JavaScript Data Types

Primitive Data Types:

Non-primitive Data Types:

Primitive Data Types:

The String Data Type:

Example:

Example:

The Number Data Type:

Example:

Example:

The Boolean Data Type:

Example:

The Undefined Data Type:

Example:

The Null Data Type:

Example:

Example:

Non-primitive Data Type:

The Object Data Type:

Example:

The Array Data Type:

Example:

The typeof Operator:

Example:

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