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 |
!= | 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”.