JS Variables and Data Types

JavaScript Variables and Data Types

JavaScript Data Types

In JavaScript there are the following types of data:

  1. String data type. Are strings between apostrophes or quotation marks.
  2. Numbers data type. Are data type integer or decimal.
  3. Boolean data type. There are two boolean values: true and false.
DescriptionExample
String“String example” or ‘String example’
Numbers35, -35, 36.50
Booleantrue or false

JavaScript Variables

The variables are declared in JavaScript with the keyword var.

  • In JavaScript is not required to declare a variable type. You need to write just the variable name. Variable type will be given after an assignment.
<script type="text/javascript">
<!--
var a;
var b;
//-->
</script>
  • In JavaScript you can declare several variables in the same var, but the statements must be separated by commas.
<script type="text/javascript">
<!--
var a, b, c;
//-->
</script>
  • When you declare a variable in JavaScript, you can assign an initial value the declared variable.
<script type="text/javascript">
<!--
var a = "Result";
var b;
b = 100;
document.write(a);
document.write("=");
document.write(b);
//-->
</script>
Result
Result = 100

JavaScript Reserved Words:

These are JavaScript reserved words and can not be used as names of functions, objects or methods.

abstract
boolean
break
byte
case
catch
char
class
const
continue
debugger
default

delete
do
double
else
enum
export
extends
false
final
finally
float
for

function
goto
if
implements
import
in
instanceof
int
interface
long
native
new

null
package
private
protected
public
return
short
static
super
switch
synchronized
this

throw
throws
transient
true
try
typeof
var
void
volatile
while
with