In HTML 4, the type attribute is required. In my experience, all
browsers will default to text/javascript if it is absent, but that
behaviour is not defined anywhere. While you can in theory leave it
out and assume it will be interpreted as JavaScript, it's invalid
HTML, so why not add it.

In HTML 5, the type attribute is optional and defaults to
text/javascript

Use <script type=text/javascript> or simply <script> (if omitted, the type is the same). Do not use <script language=JavaScript>; the language attribute is deprecated

Ref :

http://social.msdn.microsoft.com/Forums/vstudio/en-US/65aaf5f3-09db-4f7e-a32d-d53e9720ad4c/script-languagejavascript-or-script-typetextjavascript-?forum=netfxjscript

and

Difference between <script> tag with type and <script> without type?

Do you need type attribute at all?

I am using HTML5- No

I am not using HTML5 - Yes