Published on: January 25 2018

Standard JavaScript  data types include:

• Boolean

• Null

• Undefined

• Number

• String

• Object

​

Boolean

Booleans are true and false,  often used for conditional statements. they are standard across all languages,

Example:

function isNotEmpty(array){

   let len=array.length; 

   if(len>0){
     return true;
   }else{return false;}

}

​

The code above can also be written as :

​

function isNotEmpty(array){

   let len=array.length; 

   return len>0;

}
 

or

​

function isNotEmpty(array){

  return array.length>0;

}

​

Null and Undefined

Null and undefined sometime seem to be the same, but this is not actually true. Lets look at  the differences and similarities between null and undefined in JavaScript.

 

null?

You need to understand that:

• null is an empty or non-existent value.

• null must be assigned.

 

Example:

let number= null;

console.log(number);

 

output:

// null

​

​

Undefined?

Undefined is  scenario where you declare  a variable , without not defining it. For Example:

var name;

console.log(name); 

​

output:

// undefined

or

var name = undefined;

console.log(c);

output:

// undefined

​

Numbers

Number data type consists of integers and float, it handles normal numbers

(1, 12, 304, 41), negative numbers and decimal places.

 

Example:

let data = 55;

console.log(typeof data);

output:

// number

​

let data = -278;

console.log(typeof data);

output:

// number

​

let data = 1220.3;

console.log(typeof data);

output:

// number

​

​

​

Strings

Strings in JavaScript and other languages are a group of characters.

They are written inside quotes. You can use single  ' ' or double   " "quotes:

​

Examples of strings are:

var theString= "I love coding ";

var theString1= "Javascripts,  is interesting";

var theString2= 'This is a long strings';

Read More on strings :

​

Objects

Objects are a little bit of a complex  data type;

In most cases,  objects will look like the structure below:

​

var color = {

   'red': [255, 0, 0];

   'blue': [0, 0, 255];

   'green': [0, 0, 255]

}; 

​

var c = new color();

console.log(c.red)

​

output:

// [255, 0, 0];

​

One can make a copy of the color object as below:

​

var color_copy= color;
document.getElementById('demo').innerHTML=color_copy;

​

output:

// { "red": [ 255, 0, 0 ], "blue": [ 0, 0, 255 ], "green": [ 0, 0, 255 ] };

​

Then we can change the content  of the color object (Because, objects are mutable) as below:

​

color_copy.black = [0, 0, 0]; 
document.getElementById('demo').innerHTML=color_copy;

​

output:

{ "red": [ 255, 0, 0 ], "blue": [ 0, 0, 255 ], "green": [ 0, 0, 255 ], "black": [ 0, 0, 0 ] }

​

​

Read More on Objects :