= is used to assign values.
+ is used to add values
The assignment operator = is used to assign values to JavaScript
variables.The arithmetic operator + is used to add values together.
JavaScript Arithmetic Operators
Arithmetic operators are used to perform arithmetic between variables and/or values.The table below explains the arithmetic operators:
Operator
|
Description
|
Example
|
Result
|
|
+
|
Addition
|
x=y+2
|
x=7
|
y=5
|
-
|
Subtraction
|
x=y-2
|
x=3
|
y=5
|
*
|
Multiplication
|
x=y*2
|
x=10
|
y=5
|
/
|
Division
|
x=y/2
|
x=2.5
|
y=5
|
%
|
Modulus (division remainder)
|
x=y%2
|
x=1
|
y=5
|
++
|
Increment
|
x=++y
|
x=6
|
y=6
|
x=y++
|
x=5
|
y=6
|
||
--
|
Decrement
|
x=--y
|
x=4
|
y=4
|
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=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;
txt2="nice day";
txt3=txt1+txt2;
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:txt2="nice day";
txt3=txt1+txt2;
txt1="What a very";
txt2="nice day";
txt3=txt1+" "+txt2;
After the execution of the statements above, the variable txt3 contains:txt2="nice day";
txt3=txt1+" "+txt2;
"What a very nice day"
Adding Strings and Numbers
The rule is: If you add a number and a string, the result will be a string!syntax
x=10+10;
document.write(x);
x="10"+"10";
document.write(x);
x=10+"10";
document.write(x);
x="10"+10;
document.write(x);
document.write(x);
x="10"+"10";
document.write(x);
x=10+"10";
document.write(x);
x="10"+10;
document.write(x);
Example
<html>
<body>
<script type="text/javascript">
var x;
x=10+10;
document.write(x);
document.write("<br />");
x="10"+"10";
document.write(x);
document.write("<br />");
x=10+"10";
document.write(x);
document.write("<br />");
x="10"+10;
document.write(x);
document.write("<br />");
</script>
<p>The rule is: If you add a number and a string, the
result will be a string.</p>
</body>
</html>
Result:
20
1010
1010
1010
The rule is: If you add a number and a string, the result will be a string.1010
1010
1010
JavaScript Comparison and Logical Operators
Comparison and Logical operators are used to test for true or false.
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
|
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.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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