Basic callback examples

callback.js

var l = 5,
    b = 5;

function sayHello(greeting){
    greeting(function(){
        return 'Hello world'
    });
}

function area1(x,y,callback){
    callback(function(){
        return (x*y);
    });
}

function area2(x,y,callback){
    callback(
        {
            area:function(){
                return (x*y);
            }
        }    
    )
}

function area3(x,y,callback){
    callback(
       function(){
           console.log ('Ready: ' + x*y);
       }   
    )
}

sayHello(function (greeting) {
    console.log(greeting());
});

area1(l,b,function(returned){
    console.log('Ready: '+ returned());
});

area2(l,b,function(returned){
    console.log('Ready: '+ returned.area());
});

area3(l,b,function(returned){
    returned();
});

//Callback: Calling a function having as parameter other function.