Why does Javascript's OR return a value other than true/false?

Question

I saw this construction in order to get the browser viewport width:

function () { return window.innerWidth || document.documentElement.clientWidth || documen         


        

Answer 1

The JavaScript operator || is defined to return the left value if it evaluates to a truthy value, otherwise the right value instead of returning true itself. That's just how it's defined in the spec.

I know it can be annoying at times, you might accidentally end up holding a reference to something you don't want to hold on to, but it also allows for the handy trick your example has. Everything has its pros and cons.