Sunday, 3 June 2018

Chaudhari Karan

JavaScript – Syntax

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JavaScript – Syntax

Hello friends, In this lecture we will discuss syntax of JavaScript.
JavaScript – Syntax

JavaScript using statements <script>... </script> HTML tags in a web page. JavaScript code placed between these tags.

JavaScript tags can place anywhere in web page, but it is recommended that should keep in <head> tags.

Example of JavaScript Tags:
JavaScript Tags

Two important attributes of script tag:

  • Language: This attribute specifies which scripting language are using. Its value will be JavaScript. But HTML and XHTML  have phased out the use of this attribute.
  • Type: This attribute is recommended to indicate the scripting language in use and its value set to "text/javascript".

So here is JavaScript syntax:

JavaScript Tags

First JavaScript Code

This is a sample example to print out "Hello World". It is added the optional HTML comment which is surrounds to JavaScript code. It is save the code from a browser that does not support JavaScript.
JavaScript comment ends with the “//-->”. In this program document.write function used for print.

JavaScript Code

JavaScript Print

Whitespace and Line Breaks

JavaScript language is ignores tabs, spaces, and newlines. That spaces, tabs, and newlines freely in program. It is free to format and indent program.

Semicolons are Optional

JavaScript simple statement are followed by a semicolon character, like C, C++, and Java. JavaScript allows  to omit this semicolon if statements are placed on a separate line.

JavaScript Semicolons

When formatted in a single line

JavaScript Semicolons

Case Sensitivity

JavaScript is the case-sensitive language. which means the keywords, variables, function names, and any other identifiers typed with a consistent capitalization of letters.

Example: Time and TIME are convey different meanings.

Comments in JavaScript

JavaScript supports C and C++-style comments.
  • Any text between a // is treated as a comment until the end of the line and it is ignored by JavaScript.
  • Any text between the/* and */ is a comment. It may span multiple lines.
  • HTML opening comment <!—also recognizes JavaScript. It is a single line comment like //.
  • HTML closing comment  --> is not recognized by JavaScript, but it written as //-->.

Comments in JavaScript

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