Javascript Tutorial 6: JavaScript Operators and If...Else

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.

Example

Assign values to variables and add them together:

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

The result of x will be:

7

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 of x	Result of y
+	Addition	x=y+2	7	5
-	Subtraction	x=y-2	3	5
*	Multiplication	x=y*2	10	5
/	Division	x=y/2	2.5	5
%	Modulus (division remainder)	x=y%2	1	5
++	Increment	x=++y	6	6
		x=y++	5	6
--	Decrement	x=--y	4	4
		x=y--	5	4

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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=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

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The + Operator Used on Strings

The + operator can also be used to add string variables or text values together.

Example

To add two or more string variables together, use the + operator.

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

The result of txt3 will be:

What a verynice day

To add a space between the two strings, insert a space into one of the strings:

Example

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

The result of txt3 will be:

What a very nice day

or insert a space into the expression:

Example

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

The result of txt3 will be:

What a very nice day

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Adding Strings and Numbers

Adding two numbers, will return the sum, but adding a number and a string will return a string:

Example

x=5+5;
y="5"+5;
z="Hello"+5;

The result of x,y, and z will be:

10
55
Hello5

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

JavaScript If...Else

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	Description	Comparing	Returns
==	is equal to	x==8	false
		x==5	true
===	is exactly equal to (value and type)	x==="5"	false
		x===5	true
!=	is not equal	x!=8	true
!==	is not equal (neither value or type)	x!=="5"	true
		x!==5	false
>	is greater than	x>8	false
<	is less than	x<8	true
>=	is greater than or equal to	x>=8	false
<=	is less than or equal to	x<=8	true

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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) x="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

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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

Example

If the variable age is a value below 18, the value of the variable voteable will be "Too young, otherwise the value of voteable will be "Old enough":

voteable=(age<18)?"Too young":"Old enough";