Can I run arbitrary javascript code in the javascript:void() function using the browser's address bar?

Question

I was wondering if I could run a block of code(which includes for loops and if statements) in a javascript:void() function through the URL box.

Answer 1

yes, you can run statements in url box.

like this:

javascript:if(2>1){alert('2 > 1');}

Answer 2

void isn't a function, it's an operator. This means you can use it with or without parenthesis. All it does is makes the expression following it return undefined. In the case of navigation, returning undefined prevents the result of the expression from causing navigation away from the page.

You can run any JavaScript code through the address bar of your browser, whether you use the void operator or not. void just makes it safe to do so without navigating away. A popular alternative to void is to wrap your code in a self executing anonymous function:

javascript:(function () { alert("hello"); })();

Often, snippets of code like this are saved as a bookmark so that they can be run at the click of a link in the bookmarks or favourites bar on any page. These snippets are referred to as Bookmarklets.

You can read more about void in another answer I gave a while ago: http://stackoverflow.com/questions/2863878/help-me-understand-javascriptvoidnull/2864019#2864019.