In JavaScript, there are words that are used for specific purposes. These are keywords and reserved words.

Keywords in JavaScript

Keywords cannot be used as identifiers (variable names, function names, and loop labels) in JavaScript code.
This is a list of key words:

break
case
catch
continue
default
delete
do
else
finally
for
function
if
in
instanceof
new
return
switch
this
throw
try
typeof
var
void
while
with

Reserved words in JavaScript

There is also a set of words in JavaScript that are treated as reserved words. They are not currently in use but are reserved for future use.
This is a list of reserved words:

abstract
boolean
byte
char
class
const
debugger
double
enum
export
extends
final
float
goto
implements
import
int
interface
long
native
package
private
protected
public
short
static
super
synchronized
throws
transient
volatile