var str = "string";
var num = 123;
var boo = false;
var obj = {h:3};

console.log(String(str));  // "string"
console.log(Number(str));  // NaN
console.log(Boolean(str)); // true
console.log(Object(str));  // "string"

console.log(String(num));  // "123"
console.log(Number(num));  // 123
console.log(Boolean(num)); // true
console.log(Object(num));  // 123

console.log(String(boo));  // "false"
console.log(Number(boo));  // 0
console.log(Boolean(boo)); // false
console.log(Object(boo));  // true

console.log(String(obj));  // "[object Object]"
console.log(Number(obj));  // NaN
console.log(Boolean(obj)); // true
console.log(Object(obj));  // {h:3}

// Cases with undefined and null

console.log(String(null));  // "null"
console.log(Number(null));  // 0
console.log(Boolean(null)); // false
console.log(Object(null));  // [object Object] { ... }

console.log(String(undefined));  // "undefined"
console.log(Number(undefined));  // NaN
console.log(Boolean(undefined)); // false
console.log(Object(undefined));  // [object Object] { ... }