JavaScript Syntax

Learn some important characteristics of JavaScript syntax in this section.

As mentioned in the previous chapter, JavaScript code can be written inside HTML Script Tags or in a separate file with .js extension.

<script>//Write javascript code here...</script>

Character Set

JavaScript uses the unicode character set, so allows almost all characters, punctuations, and symbols.

Case Sensitive

JavaScript is a case-sensitive scripting language. So, name of functions, variables and keywords are case sensitive. For example, myfunction and MyFunction are different, Name is not equal to nAme, etc.

Variables

In JavaScript, a variable is declared with or without the var keyword.

<script>var name = "Steve"; id = 10;</script>

Semicolon

JavaScript statements are separated by a semicolon. However, it is not mandatory to end a statement with a semicolon, but it is recommended.

<script>var one = 1; two = 2; three = 3; //three different statementsvar four = 4; //single statementvar five = "Five" //single statement without ;</script>

Whitespaces

JavaScript ignores multiple spaces and tabs. The following statements are the same.

<script>var one =1;var one   =   1;var one        =         1;</script>

Code Comments

A comment is 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 */

<script>var one =1; // this is a single line comment/* this  is multi linecomment*/var two = 2;var three = 3;</script>

String

A string is a text in JavaScript. The text content must be enclosed in double or single quotation marks.

<script>var msg = "Hello World" //JavaScript string in double quotesvar msg = 'Hello World' //JavaScript string in single quotes</script>

Number

JavaScript allows you to work with any type of number like integer, float, hexadecimal etc. Number must NOT be wrapped in quotation marks.

<script>var num = 100;var flot = 10.5;</script>

Boolean

As in other languages, JavaScript also includes true and false as a boolean value.

<script>var yes = true;var no = false;</script>

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.