Greycampus

Datatypes

JavaScript provides different data types to hold different types of values. There are two types of data types in JavaScript.

Primitive data type
Non-primitive (reference) data type

JavaScript is a dynamic type language, means the type of the variable does not need to be explicitly specified.This is because the type of the variable is dynamically assigned by the javascript engine. A variable can be declared using the keyword var. var can hold any type of values such as numbers, strings etc.

There are five types of primitive data types in JavaScript.

String- represents a sequence of characters e.g. "hello"
Number- represents numeric values e.g. 100
Boolean- represents boolean value either false or true
Undefined- represents an undefined value
Null- represents null i.e. no value at all
The non-primitive data types are:
Object- represents instance through which we can access members
Array- represents a group of similar values
RegExp- represents regular expression

Primitive data types:

String:

A string (or a text string) is a series of characters. Strings are written with quotes. They can be represented by using either of single or double quotes.

Example:

var carName = "Volvo"; // Using double quotes
var carName = 'Volvo'; // Using single quotes

Example:

<!DOCTYPE html>
<html>
<body>
<p id="demo"></p>
<script>
var carName = "Volvo";
var answer = 'Its alright';
document.getElementById("demo").innerHTML =
carName + "<br>" +
answer;
</script>
</body>
</html>

Output:

Volvo
Its alright

Number:

JavaScript has only one type of numbers. Numbers can be written with, or without decimals.

Example:

var x1 = 34.00; // Written with decimals
var x2 = 34; // Written without decimals

Note: Extra large or extra small numbers can be written with scientific (exponential) notation.

Example:

<!DOCTYPE html>
<html>
<body>
<p id="demo"></p>
<script>
var x1 = 34.00;
var x2 = 34;
var y = 123e5;
var z = 123e-5;
document.getElementById("demo").innerHTML = x1 + "<br>" + x2 + "<br>" + y + "<br>" + z
</script>
</body>
</html>

Output:

34
34
12300000
0.00123

Boolean:

Booleans can only have two values: true or false.

Example:

var x = true;
var y = false;
Booleans are often used in conditional testing.

Non-primitive data types:

Arrays

JavaScript arrays are written with square brackets. The items in the Array are separated by commas.

Example:

<!DOCTYPE html>
<html>
<body>
<p id="demo"></p>
<script>
var cars = ["Saab","Volvo","BMW"];
document.getElementById("demo").innerHTML = cars[0];
</script>
</body>
</html>

Output:

saab


    
        <div style="background:#eeeeee;border:1px solid #cccccc;padding:5px 10px;"><script><br />
/*<br />
JavaScript program to take input a sequence of numbers from user and store it in a list or array<br />
Input<br />
3<br />
11<br />
12<br />
13<br />
Output<br />
[11, 12, 13]<br />
*/<br />
//message variable<br />
var msg = 'enter the number of variables';<br />
//printing message<br />
//getting user input<br />
var a = prompt(msg);<br />
var num = [];<br />
for (var i = 0; i < a; i++) {<br />
  num[num.length] = prompt('enter elements');<br />
}<br />
document.write('The elements are: '+num);<br />
</script><br />
              <br />
<script>
/*
JavaScript program to take input a sequence of numbers from user and store it in a list or array
Input
3
11
12
13
Output
[11, 12, 13]
*/
//message variable
var msg = 'enter the number of variables';
//printing message
//getting user input
var a = prompt(msg);
var num = [];
for (var i = 0; i < a; i++) {
  num[num.length] = prompt('enter elements');
}
document.write('The elements are: '+num);
</script></div>

        Try

Objects

JavaScript objects are written with curly braces.
Object properties are written in key:value pairs, which are separated by commas.

Example:

<!DOCTYPE html>
<html>
<body>
<p id="demo"></p>
<script>
var person = {
firstName : "John",
lastName : "Doe",
age : 50,
eyeColor : "blue"
};
document.getElementById("demo").innerHTML =
person.firstName + " is " + person.age + " years old.";
</script>
</body>
</html>

Output:

John is 50 years old

The object (person) in the example above has 4 properties: firstName, lastName, age, and eyeColor.


    
        <script>
/*
JavaScript program for initializing a dictionary or hash and print the second key value pair
Ouput
2->PHP
*/
var b = {1:'Ruby',2:'PHP',3:'C',4:'C++',5:'Python'};
//printing the key and value using dictionary keys() and values() functions
var keys =[];
//getting keys of hash array
for (var key in b){
  keys.push(key)
}
document.write(keys[1]+' -> '+b[keys[1]]);
</script>

        Try


    
        <script>
  /*
JavaScript program to print the type of data

Output
number
number
string
*/
//initialize the values of a,b,c with different types
a = 1
b = 1.0
c = 'Grey Campus'
d = true;
//printing types of a,b,c,d
document.write(typeof(a)+'<br>');
document.write(typeof(b)+'<br>');
document.write(typeof(c)+'<br>');
document.write(typeof(d)+'<br>');
</script>

        Try