JavaScript Data Types

Primitiv data types

In JavaScript we find a number of primitiv data types:

Boolean

Null

Undefined

Number

String

Symbol (this is new in ECMAScript 6)
In addition we have:

Object

Learn more about JavaScript Booleans Learn more about JavaScript Strings Learn more about JavaScript Numbers Learn more about JavaScript Dates

Composite Data Types

The existing composite (reference) data types in JavaScript are:

Object

Array

Special Data Types

The existing special data types in JavaScript are:

Null

Undefined

String Data Type

The existing special data types in JavaScript are:

Null

Undefined

A string is a combination of Unicode characters (letters, digits, and punctuation marks). A string usually represent a text in JavaScript and it's single or double quotation marks. Double quotation marks can be used in strings surrounded by single quotation marks. Single quotation marks can be used in strings surrounded by double quotation marks:

"Hallo there; today is friday!"
'"This is a nice car!" said the old man.'
"99"
'y'

Learn more about JavaScript Objects and Arrays

JavaScript does not have a type for just one single character. This is solved by using a string of only one character.

Number Data Type

JavaScript number can be either an integer or a floating-point values. In JavaScript, there is no distinction between them.

Integer Values

Integer values can be represented as positive whole numbers, negative whole numbers, in addition to 0. They can be in base 10 (decimal), base 16 (hexadecimal), and base 8 (octal). Usually the numbers in JavaScript are written in decimal.

Floating-point Values

Floating-point values can represented as whole numbers with decimals. They can also be expressed in scientific notation and that means as an uppercase or lowercase "e" is used as "ten to the power of".

Number	Description	Decimal Equivalent
.0001, 0.0001, 1e-4, 1.0e-4	Four equivalent floating-point numbers.	0.0001
3.45e2	A floating-point number.	345
45	An integer.	45
0378	An integer. Although this looks like an octal number (it begins with a zero), 8 is not a valid octal digit, so the number is treated as a decimal.	378
0377	An octal integer. Notice that although it only appears to be one less than the number above, its actual value is quite different.	255
0.0001	A floating point number. Even though this begins with a zero, it is not an octal number because it has a decimal point.	0.0001
00.0001	This is an error. The two leading zeros mark the number as an octal, but octals are not allowed a decimal component.	N/A (compiler error)
0Xff	A hexadecimal integer.	255
0x37CF	A hexadecimal integer.	14287
0x3e7	A hexadecimal integer. Notice that the 'e' is not treated as exponentiation.	999
0x3.45e2	This is an error. Hexadecimal numbers cannot have decimal parts.	N/A (compiler error)

JavaScript also have numbers with special values. These are:

NaN (not a number).
Positive Infinity.
Negative Infinity.
Positive and Negative 0.

Learn more about JavaScript Numbers

Boolean Data Type

The string and number data types can have an unlimited number of different values. The Boolean data type can only have two different values and they are the literals `true` and `false`. A Boolean value will specify if a condition is true or false.

Comparisons you make in your scripts always have a Boolean outcome. Consider the following line of JavaScript code.

//How to use boolean values in a control structure.
if (x == 100) {
    z = z + 1;
}
else {
    x = x + 1;
}

Learn more about JavaScript Booleans

The null Data Type

In JavaScript the data type `null` has only one value and that is: null.

A variable that contains null has no valid Number, String, Boolean, Array, or Object. It is possible to erase the content of a variable by assigning it to null without erasing the variable.

As in C and C++ null is the same as 0.

Undefined data type

Example of the undefined data type in JavaScript

JS JavaScript - Undefined data type

var x;
 
// This method works.
if (x == undefined) {
    document.write ( "comparing x to undefined <br/>");
} 
 
// This method doesn't work - you must check for the string "undefined".
if ( typeof (x) == undefined) {
    document.write ( "comparing the type of x to undefined <br/>" );
}
 
// This method does work.
if ( typeof (x) == "undefined") {
    document.write ( "comparing the type of x to the string 'undefined'");
}
 
// Output:  
// comparing x to undefined
// comparing the type of x to the string 'undefined'

Check this out

JS JavaScript: Variables

A variable contains a value. When you use the variable, you refer to the data it represents. You use variables to store, retrieve and manipulate values in your code.

JS JavaScript: Events

Events are actions or occurrences that happen to HTML elements.

JavaScript can act when an HTML Event occurs.

Events can represent everything from basic user interactions to automated notifications of things happening in the rendering model.

JS JavaScript: Numbers Methods

Number methods can help you when working with number datatypes. The number methods are improved in ES6 (ECMAScript 6).

Keep reading to understand how the number methods and properties may help you.

JS JavaScript: Errors

There will be errors in the code. It is good practice to handle exceptions/errors.

Exceptions are a type of error that occurs during the execution of an application. Errors should be logged. Sometimes it is possible to recover a bug and proceed.
Other cases the user should get inform....

JavaScript is one of the 3 core language technologies of the World Wide Web that all web developers must learn:
1.      HTML to define the content of web pages.
2.      CSS to specify the layout of web pages.
3.      JavaScript to program the behavior of web pages.

JavaScript is a scripting or programming language that allows you to implement complex things on web pages. Every time a web page does more than just sit there and display static information for you to look at, displaying timely content updates, interactive maps, animated 2D/3D graphics, scrolling video jukeboxes, etc. − you can bet that JavaScript is probably involved.

The benefits of using JavaScript are:
1.      You can validate user input before sending the page off to the server. This saves server traffic, which means less load on your server.
2.      Immediate feedback to the visitors − They don't have to wait for a page reload to see if they have forgotten to enter something.
3.      Increased interactivity − You can create interfaces that react when the user hovers over them with a mouse or activates them via the keyboard.
4.      Richer interfaces − You can use JavaScript to include such items as drag-and-drop components and sliders to give a Rich Interface to your site visitors.

Need more Honney

NDC Conferences

The NDC Conferences (Norwegian Developers Conference) are one of the world`s largest independent software conferences for .NET & Agile development. The conference covers everything you need to know within software development. The conferences are held each year in many places such as Oslo, Copenhagen, London, Sydney and Minnesota.

NDC Conferences

Update Conference Prague

Update Conference Prague is the biggest developer conference in the Czech Republic. The conference is offering sessions delivered by the top experts from all around the world. Their goal is to inspire the attendees and enrich their knowledge.

Update Conference Prague

Troy Hunt

Learn about Web Security from Troy Hunt. He is a really engaged speaker that frequently give talks on conferences around the world. Troy is a Microsoft MVP and you can even learn from him on some great courses on Pluralsight.

Visit Troy Hunt

W3Schools

W3Schools.com is a great education Web Site for learning web technologies. On W3Schools you may find well organized basic to advanced tutorials and references.

Visit W3Schools

Scott Hanselman

Learn about Web Technologies and new trends from Scott Hanselman. Scott Hanselman is an author of developer books and he is an engaged speaker that usually talks about the Microsoft stack. You may meet Scott on conferences around the world.

Visit Scott Hanselman

Developer Week

DeveloperWeek is one of the world’s largest developer conferences. Developer Week focus on new dev technologies, the conference have talks and workshops for newbies and experienced audience. You can attend on a Developer Week conference different places in Nothern America.

Developer Week

Honneybag blog

Learn JavaScript Debugging

24 May 2019

Searching for bugs and fixing them is called code debugging. The bugs might be difficult to diagnose and therefore it is important to have a good approach to find and fix the bugs effectively. Bugs in the code might be syntax errors or logical errors. Sometimes nothing happens when the code contains bugs and there is few indications where to search. Modern web browser includes a powerful suite of developer tools. The tools do a range of things...

Explore JavaScript Arrays

05 May 2019

Arrays are frequently used by developers. Programming languages can have slightly different implementation of arrays. An array is an object that can store a collection of items. You may say it`s a special variable that can have more than one value. The array holds many values under a single name, and you may access the values by referring to an index number. The easiest way to create....

Ultimate Guide to HTML Colors

15 April 2019

It is essential to give the user a good user experience. There are many things you should focus on, one of them is how you use colors on your website. We don't have to struggle with black and white TVs anymore. Users expect more and more and we can apply colors to everything we want. Texts, borders, backgrounds, shadows – in HTML they all can have whatever color you decide....