wacky double ampersand operator in JavaScript

It will return the right value if the left is truthy and the left value if the left is falsey, so in this example:

var four = 4;
var five = 5;
var whatever = four && five;
alert(whatever);

 
 

...it's going to give us a 5. However if you set the four variable to null it will give us null or if you set the four variable to 0 it will give us 0.