Javascript Tutorials ( Class 4 of Javascript )

JavaScript Operators

= is used to assign values.

+ is used to add values.

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The assignment operator = is used to assign values to JavaScript variables.
The arithmetic operator + is used to add values together.

y=5;
z=2;
x=y+z;

The value of x, after the execution of the statements above is 7.

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JavaScript Arithmetic Operators

Arithmetic operators are used to perform arithmetic between variables and/or values.
Given that y=5, the table below explains the arithmetic operators:

Operator    |    Description            |     Example       |       Result    |

+                    Addition                          x=y+2                     x=7            y=5
-                    Substraction                     x=y-2                      x=3            y=5
*                    Multiplication                   x=y*2                      x=10          y=5
/                     Division                           x=y/2                       x=2.5         y=5
%                   Moduls                           x=y%2                     x=1            y=5
++                  Increment                       x=++y                      x=6            y=6
--                   Decrement                      x=y--                        x=5            y=4

JavaScript Assignment Operators

Assignment operators are used to assign values to JavaScript variables.
Given that x=10 and y=5, the table below explains the assignment operators:





 Operator  |    Example   |    Same As   |   Result
 =                    x=y                                       x=5
 +=                  x+=y              x=x+y             x=15
 -=                   x-=y               x-y                   x=5
 *=                  x*=y              x=x*y               x=50
 /=                   x/=y               x=x/y                x=2
 %=                x%=y            x=x%y              x=0

           

The + Operator Used on Strings

The + operator can also be used to add string variables or text values together.
To add two or more string variables together, use the + operator.

txt1="What a very";
txt2="nice day";
txt3=txt1+txt2;

After the execution of the statements above, the variable txt3 contains "What a verynice day".
To add a space between the two strings, insert a space into one of the strings:


txt1="What a very ";
txt2="nice day";
txt3=txt1+txt2;

or insert a space into the expression:

After the execution of the statements above, the variable txt3 contains:
"What a very nice day"

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Adding Strings and Numbers

The rule is: If you add a number and a string, the result will be a string!

x=5+5;
document.write(x);

x="5"+"5";
document.write(x);

x=5+"5";
document.write(x);

x="5"+5;
document.write(x);

JavaScript Comparison and Logical Operators

Comparison and Logical operators are used to test for true or false.

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Comparison Operators

Comparison operators are used in logical statements to determine equality or difference between variables or values.
Given that x=5, the table below explains the comparison operators:





Operator |  Descriptioin                                           |    Example
==               is equal to                                                  x==8 is false
                                                                                       x==5 is true
===             is exactly equal to (value and type           x===5 is true
                                                                                       x==="5" is false
!=                 is not equal                                                x!= 8 is true
>                  is greater than                                           x>8 is false
<                  is less than                                                 x<8 is true
>=                is greater than or equal to                        x>=8 is false
<=                is less than or equal to                              x<=8 is true 

How Can it be Used

Comparison operators can be used in conditional statements to compare values and take action depending on the result:

if (age<18) document.write("Too young");

You will learn more about the use of conditional statements in the next chapter of this tutorial.

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Logical Operators

Logical operators are used to determine the logic between variables or values.
Given that x=6 and y=3, the table below explains the logical operators:

Operator    |     Description        |   Example                                   
&&                   and                        (x<10 && y>1) is true
||                        or                           (x==5 || y ==5 is false
!                        not                         !(x==y) is true

Conditional Operator

JavaScript also contains a conditional operator that assigns a value to a variable based on some condition.

Syntax

variablename=(condition)?value1:value2

Example

greeting=(visitor=="PRES")?"Dear President ":"Dear ";

If the variable visitor has the value of "PRES", then the variable greeting will be assigned the value "Dear President " else it will be assigned "Dear".






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