values converted to a boolean

JavaScript has a boolean type, with possible values true and false (both of which are keywords.) Any value can be converted to a boolean according to the following rules:
false, 0, empty strings (""), NaN, null, and undefined all become false.
All other values become true.
 
You can perform this conversion explicitly using the Boolean() function:

Boolean(""); // false
Boolean(234); // true

@reference_0_mozilla