Functional way for a if statement

is.js

// Just to be sure ;)
if (!Boolean.prototype.is)
{
  Boolean.prototype.is = function(fun /*, thisArg */)
  {
    'use strict';

    if (this === void 0 || this === null){
      throw new TypeError();
    }
    var type = typeof fun;
    if (type !== 'function'){
      throw new TypeError(type + " is not a function");
    }

    var thisArg = arguments.length >= 2 ? arguments[1] : void 0;

    if(this){
      return fun.call(thisArg);
    }

    return this;
  };
}

var aBool = true;

if(aBool){
  alert("it is");
}

// Even better
aBool.is(function(){
  alert("It is better ?");
});

// Chaining possible
aBool.is(function(){
  alert("It is better ?");
  return  ttrue;
}).is(function(){
  alert("It is worse ?");
  return  false;
});