[Tutorial] Javascript intruduction

`Rοmeο · November 11, 2012

Javascript intruduction

Before you start with Javascript you should know

-Perfect HTML

-CSS

Introduction

Javascript is one of the most popular scripting language in the world it is the programming language of the web for servers, PCs...

Javascript is scripting language a scripting language is a lightweight programming language

Javascript can write directly to HTML output stream react to HTML events and test HTML from input delete and create HTML elements

How to insert javascript in document

There are 3 ways to insert javascript code in document

1.In head tag

Write this in head tag

<script type="text/javascript"></script>

And here is example document

<html>
<head>
<script type="text/javascript">alert(0);</script>
</head>
<body>
</body>
</html>

Insert in body tag (the same as in head tag but code is write in between body tag)

Write this in the body tag

<html>
<head>
<script type="text/javascript">alert(0);</script>
</head>
<body>
</body>
</html>

Insert in body tag (the same as in head tag but code is write in between body tag)

Write this in the body tag

<script type="text/javascript"></script>

Here is example

<html>
<head>
</head>
<body>
<script type="text/javascript">alert(0);</script>
</body>
</html>

Insert from external file

Like in CSS

Write this in body tag

<script src="scripts.js"></script>

and write the scripts in this document

Manipulating HTML elements

You should give to your elements id for example

<p id="demo">Paragraph</p>

And use script ot manipulate the element

document.getElementById("demo").innerHTML="My first javascript";

So your code should look like this

<p id="demo">Paragraph</p>

<script>
document.getElementById("demo").innerHTML="My first javaScript";
</script>

When javascript is executed by the web browser in this case the browser will access the html element (id="demo") and replace its content innetHTML with "My first javascript" or what you have write

Write to the document output

write this code

document.write("<p> My first paragraph with javascript</p>");

Use document.write() to write direcly into the document output if you use document.write() after document has finish loading the entire HTML page will be overwritten

Statements

In javascript statements are commands to the browser the purpose of the statements is to tell the browser what to do

Example

document.getElementById("demo").innerHTML="Statement";

This statement tells to the browser to write "Statement" inside an HTML element with id="demo"

!Javascript is case sensitie there is different between function getElementById and getElementbyID or myVariable and MyVariable also javascript ignores extra spaces you can add white space ot your script to make it more readable example :

var name ="gagd"; 
var name = "fsdfs";

!

Varialbes

variable are containers for storing information

example

var number1 = 1;
var number2 = 2;
var number3 = 3;
var total = number1   number2   number4;

In javascript there is only one type variable (not like c for example)

example :

var pi = 3.14;
var name = "fname lname";
var c = 'asdad';

and one example about variable

<p id="demo"></p>
var motor="Yamaha";
document.getElementById("demo").innerHTML=motor;

Javascript operators

Addition x=2 2

- Subtraction x=5-2

* Multiplication x=3*2

/ Division x=4/2

% Modulus (division remainder) x=5%2 (result for x 1 result for y 5) lets say that y=5

Increment x= y ( result for x 9 result for y 9)lets say that y=5

-- Decrement decrement x=--y (result for =5 result for y =4)lets say that y=5

= x=y

<= x<=y

>= x>=y

= x =y same as x=x y

-= x-=y same as x=x-y

*= x*=y same as x=x*y

/ x/=y same as x=x/y

%= x%=y same as x=x%y

[Tutorial] Javascript intruduction

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