Question

While trying to understand how a web server worked, I came accross this:

//myfile.js
function donothing(){};

//myfile.html
javascript:donothing(open('http://www.acme.com/whatever.jpg','','left=100, right=0, top=100, scrollbars=no, status=no, titlebar=no, resizable=no, toolbar=no, menubar=no, width=255, height=255'))

I’m no JavaScript expert, so I don’t get how an empty function can be made to work. Does someone know?

Thank you.

Answer 1

This is a homemade void substitute to avoid having the expression return a value.

window.open will return a reference to the opened window, and this can have unexpected results.

For instance, try pasting javascript:a=1 into the address field – this will result in a blank screen with the number 1 in it as the browser will by default try to use the result of any expression run as the new document.

To avoid this you use javascript:void(a=1) as void will not return anything, and so the result isn’t used as the new document.

Using donothing(foo=bar) or the equivalent Function.prototype(foo=bar) is not needed as the built-in void does the exact same.

But mind, the use of void is only needed when copying text into the address field, its not necessary when you use the pseudo protocol javscript: in links (which you should never do anyway).