JavaScript Overview:
Learn some important characteristics of JavaScript syntax in this section.
Character Set:
JavaScript uses the Unicode character set and so allows almost all characters, punctuations, and symbols.
Case Sensitive:
JavaScript is a case sensitive scripting language. It means functions, variables and keywords are case sensitive. For example, VAR is different from var, John is not equal to john.
String:
String is a text in JavaScript. A text content must be enclosed in double or single quotation marks.
Example: string
<script>
"Hello World" //JavaScript string in double quotes
'Hello World' //JavaScript string in single quotes
</script>
Number:
JavaScript allows you to work with any kind of numbers like integer, float, hexadecimal etc. Number must NOT be wrapped in quotation marks.
Integer: 1000
Float: 10.2
Boolean:
As in other languages, JavaScript also includes true or false as a boolean value.
Semicolon:
JavaScript statements are separated by a semicolon. However, it is not mandatory to end every statement with a semicolon but it is recommended.
For example, JavaScript considers three different statements for following:
one = 1; two=2; three=3;
White space:
JavaScript ignores multiple spaces and tabs.
The following statements are same.
Example: JavaScript ignores whitespaces
var one =1;
var one = 1;
var one = 1;
Comments:
A comment is a single or multiple lines, which give some information about the current program. Comments are not for execution.
Write comment after double slashes // or write multiple lines of comments between/* and */
Example: code comment
var one =1; // this is a single line comment
/* this
is multi line
comment*/
var two = 2;
var three = 3;
Keywords:
Keywords are reserved words in JavaScript, which cannot be used as variable names or function names.
The following table lists some of the keywords used in JavaScript.
| Keywords
|
| var
|
function
|
if
|
| else
|
do
|
while
|
| for
|
switch
|
break
|
| continue
|
return
|
try
|
| catch
|
finally
|
debugger
|
| case
|
class
|
this
|
| default
|
false
|
true
|
| in
|
instanceOf
|
typeOf
|
| new
|
null
|
throw
|
| void
|
width
|
delete
|
Points to Remember :
- JavaScript uses unicode characterset.
- JavaScript is case sensitive.
- JavaScript string must be enclosed in double quotation mark (") or single quotation mark (').
-
JavaScript Number can store integer, float, hexadecimal value without enclosing it in quotation marks.
-
JavaScript boolean value stores true or false.
- Every statement in JavaScript can be separated using semicolon (;). It is not mandatory but recommended to use semicolon at the end of each statement.
- JavaScript ignores multiple white spaces.
- A multi line comment can be wrapped between /* and */. Single line comment can start with //.
- JavaScript keywords are reserved words. Do not use them as variable or function names.
