JAVASCRIPT

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Why we use java script :?

JavaScript a light weight and very fast programming language can be used in browsers to make websites more interactive, interesting, and user-friendly.

1- ACCESS CONTENT We can use JavaScript to select any element, attribute, or text from an Html page

2- MODIFY CONTENT You can use JavaScript to add elements, attributes, and text to the page, or remove them.

3- PROGRAM RULES You can specify a set of steps for the browser to follow (like a recipe), which allows it to access or change the content of a page.

4-REACT TO EVENTS You can specify that a script should run when a specific event has occurred.

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Data types :

Numbers : int , long int, double etc .

Strings : “ some thing”

Char : ‘c’

Boolean : T ,F (1,0) __

The variables :

Var …name… and then the value .

Ex .

String :

<var name= ”Aseel ”>

number:

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how can I show the value of a variable ?

Consol.log (age) .. consol.log (variable name)

Boolean : Var checked = true ;

Consol.log( checked) …. The result will be( true )

Ex. The check box 😊 . ___

How can we start our js .

Using

• **** (‘Class 04’) ;

Examples

 * console.log (‘Class 04’) ;

 * Var fname = ‘Aseel ’ we can use single quotation in Js ;
 Console.log (fname)

 * Var age = 22 ;
 Console.log (age)

 * Console.log(‘first name :’ + fname);
  (the result will be first name : Aseel)

 * Var Female = true ;
Console.log (Female)

* Console.log(‘first name :’ + fname + ’ age ’+ age +’is Female’+ Female );

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Note :

Console.log (‘5’+5+5) the result will be 555 . as a String because the first parameter was a string .. if it was an integer for example the result will integer . ____

Comments :

Single line comments start with //. Multi-line comments start with /* and end with */.

Ps : “WE can do it using CTRL and forward slash on the keyboard ” . __

How can we print it directly in html not in th consol ?

’’’

’’’ ____

Another type to show a message to the user is Alert

Why the content will not shown untel we exit the alert ? ,

Bacouse , the execution is sequinntly line by line .

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Note

If I have the result in the console and not shown in the html pages the I should know there’s a false in ordering code . Tf the result didn’t shown in both then I have error in my code .

So console is very important for developers to fix problems ,bugs And to check the outputs .
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Prompt()

Function inside it we can add message Prompt(“Whats your name ? ”);

How can we use it ??

Var fname = Prompt(“Whats your name ? ”);

Console.log (fname);

3- Var fname = Prompt(“Whats your name ? ‘DEfoult’ ”); _____

SCRIPT

A script is a series of instructions that a computer can follow to achieve a goal.

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JavaScript Arrays

JavaScript arrays are used to store multiple

1- values in a single variable.

Example

var cars = [“Saab”, “Volvo”, “BMW”];

2- Using the JavaScript Keyword new The following example also creates an Array, and assigns values to it:

Example

var cars = new Array(“Saab”, “Volvo”, “BMW”);

3- Access the Elements of an Array

You access an array element by referring to the index number.

This statement accesses the value of the first element in cars:

var name = cars[0];

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4- Changing an Array Element

This statement changes the value of the first element in cars:

cars[0] = “Opel”; ___

Expressions :

An expression evaluates into (results in) a single value. Broadly speaking there are two types of expressions.

1- ASSIGN A VALUE TO A VARIABLE

2- USE TWO OR MORE VALUES TO RETURN A SINGLE VALUE ___

OPERATORS :

1- Arithmetic Operators :

Operator	Description
<+>	Addition
<->	Subtraction
<*>	Multiplication
**	Exponentiation (ES2016)
/	Division
%	Modulus (Division Remainder)
++	Increment
–	Decrement

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2- Assignment Operators

Assignment operators assign values to JavaScript variables.

Operator	Example	Same As
=	x = y	x = y
+=	x += y	x = x + y
-= 1	x -= y	x = x - y
*=	x *= y	x = x * y
/= x	/= y	x = x / y
%=	x %= y	x = x % y
**=	x **= y	x = x ** y

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3- Logical Operators

Operator	Description
&&	logical and
II	logical or
!	logical not

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Functions

A JavaScript function is a block of code designed to perform a particular task.

A JavaScript function is executed when “something” invokes it (calls it).

Example

function myFunction(p1, p2) { return p1 * p2; // The function returns the product of p1 and p2 }