Edit in JSFiddle

//create primtives
var N = 5;
var S = 'foo';
var B = true;

//add properties to primitives, that get destroyed when wrapper is trashed
N.test = 'test';
S.test = 'test';
B.test = 'test';

//verify that non of these properties remain.
console.log(N.test); //logs undefined
console.log(S.test); //logs undefined
console.log(B.test); //logs undefined