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Friday, December 1, 2017

Variables & Javascript operators

1 - Javascript variables

1 - 1 Definition:

A Javascript variable is a container, ie it is introduced to represent or schematize a memory area or in other words an information storage location.

1 - 2 Types of Javascript variable:

Javascript includes 4 types of variables:
  1. Number      :   integer or decimal (like 5 7 2.35 ...)
  2. String         :   (like "car", "house", "tree" ...)
  3. Booleans    :  (logical value such as true or false)

To declare a variable just put the var statement followed by the name of the variable

Example :


var x=5;
//we have just defined a variable x whose value is 5
Javascript is a dynamically typed language, which means that you do not have to declare the type of the variable. let's take the following example to clear up the trick:

var x = 5;
// the type of variable x is now numeric
x = "car";
// the language automatically convert 
//the type of the numeric variable to the string type

1 -3 Concaténation de variables

Le terme concaténation signifie : juxtaposition ou  enchaînement, et ici en javascript le terme veut dire mettre une variable juste à coté de l’autre, pour concaténer deux variables on utilise le symbol  « + » :

Exemple :
var x = "auto";
var y = "bus";
var z = x + y;
// the variable z takes "autobus" as value

<script language = "javascript">
var x = 5;
window.document.write ("the value of x is" + x);
// the symbol + here plays the role of concatenation
</ Script>
What will display after execution:

the value of x is : 5 

(it is a concatenation between a variable of numeric type x = 5 and a variable of type string "the value of x is: ")

2 - Javascript operators

An operator is a symbol used to manipulate variables, that is to say, to perform and evaluate operations ... There are several types of operators: arithmetic operators, assignment operators, comparison operators, logical operators ...

2 - 1 Arithmetic operators

Calculation operators allow to mathematically modify the value of a variable
  1.   "+"   addition operator Adds two values
  2.  " -"    subtraction operator Subtracts two values
  3.   "*"   multiplication operator Multiplies two values
  4.   "/"   division operator Divides two values
  5.   "="  assignment operator Assigns a value to a variable x = 3 Put the value 3 in the variable x

2 - 2 Assignment Operators

These operators simplify operations such as adding a value to a variable and storing the result in the variable. For example: x = x + 2

With the assignment operators it is possible to write this operation in the following form: x + = 2. That is, if x = 3 it becomes after the operation 5.

  1.  "+  ="  add two values ​​and store the result in the variable (on the left)
  2. " -  = " subtracts two values ​​and stores the result in the variable
  3.  "*  = " multiplies two values ​​and stores the result in the variable 
  4. " / =" divide two values ​​and store the result in the variable

2 - 3 - Comparison Operators

= =
equality operator: returns 1 if the compared elements are equal, 0 otherwise
!=
difference operator: returns 1 if the compared elements are different, 0 otherwise
<        strict inferiority operator: returns True if the comparison is correct, False otherwise
<=
inferiority operator: returns True if the comparison is correct, False otherwise
>
strict superiority operator: returns True if the comparison is correct, False otherwise
>=
superiority operator: returns True if the comparison is correct, False otherwise
===
identity operator: compares the value and type of the variables, returns 1 if the elements compared are the same, 0 otherwise
!== difference operator: compares the value and type of the variables, returns 1 if the compared elements are different, 0 otherwise

Example given x=7;

Comparison Result
x = = 7 true
x < 3 false
x <= 7 true
x > 10 false
x >= 11 true
x != 7 false








2 - 4 - Logical operators

&&     which means   AND operator : implies that all conditions are fulfilled
||         which means   OR operator : implies that at least one of the conditions is fulfilled
       which means   Negative operator : implies that the condition is not realized









Younes Derfoufi

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Python Exercises With Solutions

  1. Exercises on Python Strings
  2. Exercises on Python lists
  3. OOP Exercices with solutions
  4. Exercises on Python File I/O
  5. Python Dictionary Exercises
  6. Python Sets Exercises
  1. Python Arithmetic Exercises
  2. Equations & System Of Equations
  3. Polynomials and Functions
  4. Python Arithmetic Exercises 
  5. Numpy, Matplolib, Sympy , Scipy - Exercises
  6. Python Arithmetic Exercises
  1. Python GUI Tkinter Exercises



Younes Derfoufi

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