JS Operators

The assignment operator = is used to assign values to JS variables.

The arithmetic operator + is used to add values together.

a=5;

b=7;

c=a+b;

The value of c, after the execution of the statements above is 12.

JS 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
–	Subtraction	x=y-2	x=3
*	Multiplication	x=y*2	x=10
/	Division	x=y/2	x=2.5
%	Modulus (division remainder)	x=y%2	x=1
++	Increment	x=++y	x=6
—	Decrement	x=–y	x=4

JS 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=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 very nice 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:

txt1=”What a very”;

txt2=”nice day”;

txt3=txt1+” “+txt2;

After the execution of the statements above, the variable txt3 contains:

“What a very nice day”

Example. Adding Strings and Numbers:

Look at this example:

<html>
<body>
<script type="text/javascript">
x=5+5;
document.write(x);
document.write("<br />");
x="5"+"5";
document.write(x);
document.write("<br />");
x=5+"5";
document.write(x);
document.write("<br />");
x="5"+5;
document.write(x);
document.write("<br>");
</script>
<p>The common rule is: If you add a number and a string,
the result will be a string.</p>
</body>
</html>

The rule is: If we add a number and a string, the result will be a string.

JS Comparison Operators

JS 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	Description	Example
==	is equal to	x==8 is false
===	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”);

JS Logical Operators

JS 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

JS Conditional Operator

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

Syntax

variable_name = (condition)?value1:value2

Example

greeting = (visitor==”PRES”) ? “Dear PM” : “Dear “;

If the variable visitor has the value of “PRES”, then the variable greeting will be assigned the value “Dear PM” else it will be assigned “Dear”.