Canonicalization, so that e.g. null and undefined turn into false and ordinary values (e.g. functions, arrays, numbers, objects) turn into true. Try putting th

Canonicalization, so that e.g. null and undefined turn into false and ordinary values (e.g. functions, arrays, numbers, objects) turn into true. Try putting things like these into the address bar of your browser: javascript:alert(!!null) javascript:alert(!!undefined) javascript:alert(!!{}) javascript:alert(!!Math.floor)