why do we need javascript: while making inline javascript calls

We have lot of legacy inline javascript code for img onclick , href clicks ets and those c开发者_开发技巧licks starts with javascript:

javascript:showpopup(); 

why do we need javascript: before calling the javascript functions.

any explanation will be appreciated.

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The javascript: scheme indicates to the browser that it's JavaScript code and not a relative path from the current page's base URL.

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For inline event handlers like onclick or onmouseover you don't need the javascript: part.

<a href="javascript:you_need_it_here();" onmouseover="but_not_here();">Link</a>

Without javascript: in the href, clicking that link would try to take you to somewhere like this:

http://www.example.com/something/you_need_it_here();

See @Ignacio's answer for the reason.