Wrap a function with a middleware decorator.

JavascriptMiddlewares.js

// Generate a middleware
function middleware(mw){
    return function(fn){
        fn = (typeof fn == "function") ? fn : window[fn];
        return function(){
            var args = arguments || [];
            if(false !== mw.apply(this,args)) fn.apply(this,args);
        };
    };
}


// Example middleware, only accept knowed people
var mustBeAquaintance = middleware(function(name){
    // check if user is logged in here
    var iKnowYou = ['Jack','Lisa'].indexOf(name)>=0;
    if( ! iKnowYou ){
        console.log(name + "? I don't know you, go away.");
        return false;
    }
});


// The naive function
var letMeIn = function(name){
    console.log("Hello "+name+", how are you?");
};

// Naive version
letMeIn('Jack');
letMeIn('Frank');
letMeIn('Lisa');

// Apply middleware
letMeIn = mustBeAquaintance(letMeIn);

console.log("\nParanoic Mode: on\n");

// Paranoic version
letMeIn('Jack');
letMeIn('Frank');
letMeIn('Lisa');